Input Validation & Sanitization - Stopping Injection Attacks

1. What is the primary purpose of input validation?

A) To prevent users from entering incorrect data
B) To protect applications from injection attacks
C) To improve user experience
D) To ensure faster application performance

✅ Answer: B) To protect applications from injection attacks
Explanation: Input validation ensures that user input is safe and conforms to expected formats, preventing malicious inputs that could lead to SQL injection, XSS, and other attacks.

2. Which of the following is the most effective way to prevent SQL Injection?

A) Using eval() to sanitize inputs
B) Using parameterized queries and prepared statements
C) Using client-side JavaScript validation only
D) Allowing unrestricted user input

✅ Answer: B) Using parameterized queries and prepared statements
Explanation: Parameterized queries ensure that user input is treated as data, not executable SQL, making SQL injection impossible.

3. Which input validation technique is most effective?

A) Blacklist-based validation
B) Whitelist-based validation
C) Encoding user input
D) Removing all special characters

✅ Answer: B) Whitelist-based validation
Explanation: Whitelist-based validation only allows expected, predefined input, preventing attacks by rejecting unexpected or malicious data.

4. How can you prevent Cross-Site Scripting (XSS) attacks?

A) Encode user input before rendering it in HTML
B) Disable JavaScript in the browser
C) Use innerHTML to insert user input directly into the page
D) Store user input in plaintext

✅ Answer: A) Encode user input before rendering it in HTML
Explanation: Encoding ensures that special characters like <, >, and " are treated as text, preventing script execution.

5. What is the main risk of relying solely on client-side validation?

A) It makes the application slower
B) It can be bypassed by an attacker
C) It increases server load
D) It is unnecessary

✅ Answer: B) It can be bypassed by an attacker
Explanation: Client-side validation can be disabled or manipulated by an attacker, making server-side validation essential.

6. Which of the following is an example of input sanitization?

A) Removing all numbers from user input
B) Escaping special characters before inserting into the database
C) Allowing all input but logging malicious attempts
D) Automatically capitalizing all user input

✅ Answer: B) Escaping special characters before inserting into the database
Explanation: Escaping ensures that special characters are treated as text rather than executable code.

7. What is the best way to prevent command injection attacks?

A) Allow users to execute system commands
B) Validate and sanitize input before passing it to system commands
C) Use eval() to process user input
D) Encode output instead of input

✅ Answer: B) Validate and sanitize input before passing it to system commands
Explanation: Command injection occurs when user input is directly passed to system commands. Proper validation and sanitization prevent attackers from injecting malicious commands.

8. Which HTTP header can help mitigate XSS attacks?

A) X-Content-Type-Options: nosniff
B) Content-Security-Policy (CSP)
C) X-Frame-Options: DENY
D) Referrer-Policy: no-referrer

✅ Answer: B) Content-Security-Policy (CSP)
Explanation: CSP restricts sources of executable scripts, reducing the risk of XSS.

9. Why is using `htmlspecialchars()` in PHP useful for preventing XSS?

A) It removes malicious scripts from user input
B) It encodes special characters like < and >
C) It blocks JavaScript entirely
D) It hashes user input

✅ Answer: B) It encodes special characters like < and >
Explanation: Encoding special characters prevents browsers from interpreting them as HTML or JavaScript.

10. What is a common mistake when implementing input validation?

A) Using client-side validation only
B) Validating input on the server
C) Using regex for validation
D) Escaping user input

✅ Answer: A) Using client-side validation only
Explanation: Client-side validation can be bypassed, so server-side validation is crucial for security.

11. Which of these statements about sanitization is true?

A) It replaces invalid characters with safe alternatives
B) It only applies to database input
C) It is a replacement for validation
D) It blocks all user input

✅ Answer: A) It replaces invalid characters with safe alternatives
Explanation: Sanitization modifies input to remove harmful elements, reducing attack risks.

12. Which OWASP Top 10 category does input validation primarily help mitigate?

A) Security Misconfiguration
B) Injection
C) Insecure Deserialization
D) Broken Access Control

✅ Answer: B) Injection
Explanation: Proper input validation prevents SQL injection, XSS, and command injection attacks.

13. What does the `bindParam()` function in PHP do?

A) Escapes input manually
B) Binds user input to a prepared SQL statement
C) Removes special characters
D) Encrypts user input

✅ Answer: B) Binds user input to a prepared SQL statement
Explanation: This prevents SQL injection by treating input as data, not executable SQL.

14. What is an insecure method of validating email input?

A) Using a regex pattern
B) Checking the input contains @
C) Using built-in email validation functions
D) Using HTML5’s type="email"

✅ Answer: B) Checking the input contains @
Explanation: A simple @ check is insufficient—valid emails must follow strict format rules.

15. Which of the following is NOT an effective method to sanitize input?

A) Using a strict allowlist
B) Removing all special characters
C) Escaping output
D) Using input validation libraries

✅ Answer: B) Removing all special characters
Explanation: Some special characters are necessary (e.g., in names like “O’Connor” or URLs).

16. Why is encoding important for preventing XSS?

A) It removes malicious scripts
B) It converts characters into safe representations
C) It blocks JavaScript execution
D) It encrypts the input

✅ Answer: B) It converts characters into safe representations
Explanation: Encoding converts characters like < into <, preventing execution.

17. Which of the following statements is true?

A) Input validation alone is enough to prevent attacks
B) Input validation should be combined with other security measures
C) Only admin users’ input should be validated
D) Allowing unrestricted user input is secure

✅ Answer: B) Input validation should be combined with other security measures
Explanation: Validation must be used with escaping, sanitization, and access controls.

18. What is the main drawback of blacklist-based validation?

A) It is slow
B) Attackers can bypass it with new payloads
C) It is too strict
D) It requires JavaScript

✅ Answer: B) Attackers can bypass it with new payloads
Explanation: A blacklist cannot anticipate every possible malicious input.

19. Why is allowing only expected characters in user input considered a good security practice?

A) It improves performance by reducing input size
B) It makes the application easier to maintain
C) It minimizes the risk of injection attacks by rejecting malicious input
D) It allows more flexibility in data handling

✅ Answer: C) It minimizes the risk of injection attacks by rejecting malicious input
Explanation: Using an allowlist (whitelist) ensures only permitted characters are accepted, reducing risks of SQL injection, XSS, and command injection.

20. Which of the following input validation techniques is the most secure?

A) Validating input at the client side only
B) Using regular expressions (regex) for pattern matching
C) Checking user input against a predefined schema on the server
D) Accepting all input and sanitizing it later

✅ Answer: C) Checking user input against a predefined schema on the server
Explanation: Schema validation ensures input follows strict rules, preventing invalid or malicious data from being processed.

21. What is the biggest limitation of using blacklist-based input validation?

A) It blocks all special characters, even safe ones
B) It requires more processing power
C) Attackers can bypass it with new techniques
D) It slows down the database queries

✅ Answer: C) Attackers can bypass it with new techniques
Explanation: Blacklists cannot anticipate all possible attack variations, making them ineffective against evolving threats.

22. Which security risk is not mitigated by input validation alone?

A) SQL Injection
B) Cross-Site Scripting (XSS)
C) Cross-Site Request Forgery (CSRF)
D) Command Injection

✅ Answer: C) Cross-Site Request Forgery (CSRF)
Explanation: CSRF exploits authenticated user sessions and requires token-based protections, not just input validation.

23. What is a secure way to handle user input for file uploads?

A) Allow users to upload any file type but scan for malware later
B) Restrict allowed file types and validate MIME types
C) Rename uploaded files with random names
D) Store uploaded files in the application’s root directory

✅ Answer: B) Restrict allowed file types and validate MIME types
Explanation: Restricting file types and verifying MIME types prevents the upload of malicious scripts or executables.

24. Which of the following input validation techniques provides the most security for passwords?

A) Allowing only alphanumeric characters
B) Using a minimum length requirement
C) Enforcing complexity rules with a strong policy
D) Hashing the password before storing it

✅ Answer: C) Enforcing complexity rules with a strong policy
Explanation: A strong password policy prevents weak passwords that attackers can easily guess or brute force.

25. How does input validation help prevent Server-Side Request Forgery (SSRF)?

A) By filtering out dangerous user inputs such as internal IP addresses
B) By escaping user input before executing commands
C) By using JavaScript to validate input fields
D) By encoding user input in database queries

✅ Answer: A) By filtering out dangerous user inputs such as internal IP addresses
Explanation: SSRF attacks exploit web applications to send requests to internal systems. Validating and restricting untrusted URLs/IPs helps prevent this.

26. Which of the following is an example of improper input validation?

A) Allowing only numeric values for an age field
B) Allowing user input to be directly executed as a database query
C) Rejecting empty input for a required field
D) Checking that an email field contains an @ character

✅ Answer: B) Allowing user input to be directly executed as a database query
Explanation: Directly executing user input in a query allows SQL injection attacks.

27. Why is encoding output essential for preventing injection attacks?

A) It prevents attackers from inserting malicious scripts into the application
B) It removes all harmful characters from user input
C) It compresses the input data for faster processing
D) It converts user input into a secure hash

✅ Answer: A) It prevents attackers from inserting malicious scripts into the application
Explanation: Encoding prevents user input from being executed as HTML or JavaScript, stopping XSS attacks.

28. Which of the following prevents both SQL Injection and XSS?

A) Using a Content Security Policy (CSP)
B) Using a Web Application Firewall (WAF)
C) Using parameterized queries and output encoding
D) Blocking all user input

✅ Answer: C) Using parameterized queries and output encoding
Explanation: Parameterized queries protect against SQL injection, and output encoding prevents XSS.

29. What is a common mistake when implementing input validation?

A) Using both client-side and server-side validation
B) Using overly restrictive rules that reject legitimate input
C) Sanitizing user input before validation
D) Logging invalid user input attempts

✅ Answer: C) Sanitizing user input before validation
Explanation: Input should be validated first and then sanitized only if needed, not before validation.

30. Which function is recommended for escaping user input in an HTML context?

A) strip_tags()
B) htmlspecialchars()
C) strtolower()
D) md5()

✅ Answer: B) htmlspecialchars()
Explanation: htmlspecialchars() converts special characters into HTML entities, preventing XSS.

31. What should be done if an input field expects a date?

A) Use a regex pattern to enforce the format
B) Convert input into a standard date format before storing it
C) Reject any input that does not match a date format
D) All of the above

✅ Answer: D) All of the above
Explanation: Validating, standardizing, and enforcing format rules ensure dates are processed correctly.

32. Which SQL statement is most vulnerable to injection?

A) SELECT * FROM users WHERE id = ?
B) SELECT * FROM users WHERE id = $_GET['id'];
C) SELECT * FROM users WHERE id = :id
D) SELECT * FROM users WHERE id = bindParam(:id)

✅ Answer: B) SELECT * FROM users WHERE id = $_GET['id'];
Explanation: Directly embedding user input in SQL queries makes them vulnerable to injection.

33. Why is client-side validation not enough?

A) Some users may not understand JavaScript errors
B) It does not work on older browsers
C) Attackers can bypass it by sending requests directly
D) It makes applications slower

✅ Answer: C) Attackers can bypass it by sending requests directly
Explanation: Client-side validation is easily bypassed, so server-side validation is crucial.

34. What should be avoided when handling user input?

A) Treating input as code
B) Filtering input
C) Encoding input
D) Validating input

✅ Answer: A) Treating input as code
Explanation: User input should never be executed as code to prevent RCE (Remote Code Execution).

35. What is the recommended method for storing user passwords?

A) Plaintext storage
B) MD5 hashing
C) bcrypt hashing with salting
D) Encoding passwords with Base64

✅ Answer: C) bcrypt hashing with salting
Explanation: bcrypt with salting makes passwords resistant to brute force attacks.

36. Why is it dangerous to use `eval()` in JavaScript when handling user input?

A) It slows down the execution speed
B) It allows users to execute arbitrary JavaScript code
C) It is not supported in modern browsers
D) It automatically escapes user input

✅ Answer: B) It allows users to execute arbitrary JavaScript code
Explanation: eval() executes input as code, making it a prime target for Remote Code Execution (RCE) and injection attacks.

37. Which type of validation should always be performed first?

A) Client-side validation
B) Server-side validation
C) Both at the same time
D) None, validation is not necessary

✅ Answer: B) Server-side validation
Explanation: Client-side validation can be bypassed, while server-side validation ensures security.

38. What is the best way to prevent LDAP injection?

A) Escape user input before inserting it into an LDAP query
B) Use parameterized LDAP queries
C) Only allow alphanumeric characters in input
D) Use client-side JavaScript to check input

✅ Answer: B) Use parameterized LDAP queries
Explanation: Parameterized queries prevent attackers from injecting LDAP expressions, just like SQL injection prevention.

39. Why is `strip_tags()` in PHP not a complete solution for preventing XSS?

A) It does not remove all types of malicious payloads
B) It removes too many characters
C) It only works on GET requests
D) It requires JavaScript to function

✅ Answer: A) It does not remove all types of malicious payloads
Explanation: Attackers can bypass strip_tags() using event handlers, encoded characters, or malformed HTML.

40. What is the most effective way to prevent Cross-Site Scripting (XSS) in a React.js application?

A) Use dangerouslySetInnerHTML
B) Use proper HTML encoding and avoid direct DOM manipulation
C) Only sanitize input on the frontend
D) Disable JavaScript in user browsers

✅ Answer: B) Use proper HTML encoding and avoid direct DOM manipulation
Explanation: Encoding ensures HTML is rendered as text, not executable script.

41. How can developers prevent input validation bypass attacks?

A) Use JavaScript to validate input
B) Implement server-side validation and enforce strict data types
C) Allow users to submit any input
D) Only validate input when an error occurs

✅ Answer: B) Implement server-side validation and enforce strict data types
Explanation: Strict data types prevent attackers from injecting unexpected input values.

42. What is an insecure practice when handling user input?

A) Accepting only predefined input formats
B) Storing user input in a temporary variable before sanitization
C) Using a validation framework
D) Accepting user input without any checks

✅ Answer: D) Accepting user input without any checks
Explanation: Unvalidated input can lead to security vulnerabilities like SQL injection and XSS.

43. What is a potential risk of JSON-based input validation?

A) JSON does not support validation
B) Attackers can manipulate JSON input to include unexpected data types
C) JSON input is always safe
D) JSON input cannot be encoded

✅ Answer: B) Attackers can manipulate JSON input to include unexpected data types
Explanation: Validating both structure and expected data types is crucial to prevent attacks.

44. How does input sanitization differ from validation?

A) Validation checks if input is expected, while sanitization modifies it to remove harmful elements
B) Sanitization and validation are the same
C) Validation only applies to numbers, while sanitization applies to text
D) Sanitization is done only on the client-side

✅ Answer: A) Validation checks if input is expected, while sanitization modifies it to remove harmful elements
Explanation: Both processes are necessary: validation ensures input is correct, while sanitization removes potentially dangerous content.

45. Which of the following is a sign of insecure input handling?

A) Using input validation libraries
B) Accepting free-form text in system commands
C) Whitelisting input
D) Restricting input based on expected formats

✅ Answer: B) Accepting free-form text in system commands
Explanation: Allowing unvalidated input in system commands leads to command injection.

46. What is the best approach to validate user-provided URLs?

A) Accept any input and remove special characters
B) Use a regex pattern that allows only well-formed URLs
C) Only allow URLs that contain “http” or “https”
D) Convert URLs to lowercase before storing them

✅ Answer: B) Use a regex pattern that allows only well-formed URLs
Explanation: Validating URL format prevents phishing attacks and malicious redirects.

47. Why is normalizing input useful in validation?

A) It converts input into a standard format before validation
B) It makes validation faster
C) It helps store data in a database efficiently
D) It ensures case sensitivity in input

✅ Answer: A) It converts input into a standard format before validation
Explanation: Normalization helps remove inconsistencies, making validation more reliable.

48. What is an example of improper sanitization?

A) Removing all spaces from user input
B) Escaping special characters before rendering output
C) Hashing passwords before storing them
D) Enforcing a strict character limit on input fields

✅ Answer: A) Removing all spaces from user input
Explanation: Blindly modifying user input can lead to unintended data corruption.

49. Which technique is commonly used to prevent NoSQL Injection?

A) Encoding user input
B) Using parameterized queries for NoSQL databases
C) Storing user input in environment variables
D) Validating input on the client-side only

✅ Answer: B) Using parameterized queries for NoSQL databases
Explanation: Parameterized queries ensure input is treated as data, not executable queries, just like in SQL.

50. What is the best way to prevent HTTP Host Header Injection?

A) Encode user input before processing
B) Allow any hostnames in the request header
C) Validate and restrict accepted hostnames on the server
D) Convert all hostnames to lowercase before storing

✅ Answer: C) Validate and restrict accepted hostnames on the server
Explanation: Host Header Injection allows attackers to manipulate server behavior, so restricting valid hostnames mitigates this risk.

51. Why is integer-based input validation important?

A) It prevents users from entering negative numbers
B) It ensures only numeric values are processed, reducing injection risks
C) It makes calculations faster
D) It converts all inputs to numbers

✅ Answer: B) It ensures only numeric values are processed, reducing injection risks
Explanation: Validating integer input prevents attacks like SQL injection by ensuring non-numeric input is rejected.

52. What is the most secure way to validate email addresses?

A) Allow any string containing @
B) Use a regex pattern for strict email format validation
C) Convert the email to lowercase before saving
D) Allow users to enter free-form text

✅ Answer: B) Use a regex pattern for strict email format validation
Explanation: A properly defined regex ensures that the email follows standard formats, reducing spam and injection risks.

53. Which HTTP method should be avoided for user input when performing sensitive operations?

A) GET
B) POST
C) PUT
D) DELETE

✅ Answer: A) GET
Explanation: GET requests expose data in the URL, making them susceptible to parameter tampering and data leakage.

54. Which of the following techniques helps prevent SQL Injection?

A) Using stored procedures with parameterized inputs
B) Concatenating user input into SQL queries
C) Using exec() to execute queries dynamically
D) Using JavaScript to validate input

✅ Answer: A) Using stored procedures with parameterized inputs
Explanation: Stored procedures with parameters ensure input is treated as data, preventing SQL injection.

55. What is the main security issue when accepting JSON input from users?

A) JSON inputs are always insecure
B) Attackers can inject malicious scripts via JSON keys or values
C) JSON input can only be validated on the client-side
D) JSON encoding is slow

✅ Answer: B) Attackers can inject malicious scripts via JSON keys or values
Explanation: Unvalidated JSON data may allow attackers to manipulate objects and inject malicious payloads.

56. How can developers prevent HTML form tampering?

A) Store critical form data in hidden fields
B) Use JavaScript to check values before submission
C) Implement server-side validation and enforce expected values
D) Allow only numeric input in text fields

✅ Answer: C) Implement server-side validation and enforce expected values
Explanation: Client-side fields (including hidden ones) can be modified, so server-side validation is essential.

57. What is a common security flaw in poorly designed CAPTCHA systems?

A) They allow automated bots to bypass security measures
B) They slow down the website
C) They require JavaScript to function
D) They do not work on mobile devices

✅ Answer: A) They allow automated bots to bypass security measures
Explanation: Weak CAPTCHA implementations can be bypassed by automated tools, allowing bots to submit malicious input.

58. What is the purpose of input length validation?

A) To reject excessively long or short input that could cause buffer overflows
B) To make the application faster
C) To prevent users from entering incorrect spelling
D) To increase server security

✅ Answer: A) To reject excessively long or short input that could cause buffer overflows
Explanation: Length validation prevents buffer overflow attacks and resource exhaustion.

59. Which input validation method is most secure for user authentication?

A) Checking only for a valid username and password
B) Implementing multi-factor authentication (MFA)
C) Using JavaScript for password validation
D) Storing passwords in plaintext

✅ Answer: B) Implementing multi-factor authentication (MFA)
Explanation: MFA adds an extra security layer beyond input validation to prevent credential-based attacks.

60. What is a risk of allowing file uploads without validation?

A) Attackers can upload and execute malicious scripts
B) The server will become slow
C) Users may upload duplicate files
D) File names will be too long

✅ Answer: A) Attackers can upload and execute malicious scripts
Explanation: Malicious files can be executed on the server, leading to Remote Code Execution (RCE).

61. Which is an effective method to prevent Command Injection?

A) Allow user input in system commands
B) Restrict input to expected formats and use parameterized functions
C) Log all user inputs
D) Allow unrestricted shell execution

✅ Answer: B) Restrict input to expected formats and use parameterized functions
Explanation: User input should never be passed directly to system commands.

62. Why is `Content-Type` validation necessary when handling user input?

A) To ensure input is processed correctly based on its MIME type
B) To improve website performance
C) To reduce image file sizes
D) To prevent users from modifying requests

✅ Answer: A) To ensure input is processed correctly based on its MIME type
Explanation: Incorrect Content-Type values may allow attackers to bypass validation and upload malicious files.

63. What is a common flaw in poorly implemented password reset forms?

A) They require a strong password
B) They send a reset link without verifying identity
C) They allow users to reset passwords only once
D) They force users to reset passwords too often

✅ Answer: B) They send a reset link without verifying identity
Explanation: Without verifying the requestor, an attacker can reset another user’s password.

64. What is the risk of allowing unrestricted Unicode input?

A) Attackers can insert invisible characters to manipulate data
B) Unicode makes input validation harder
C) Some languages are not supported
D) Unicode is not recognized by all browsers

✅ Answer: A) Attackers can insert invisible characters to manipulate data
Explanation: Certain Unicode characters can be used to hide malicious payloads.

65. Why should form fields use `maxlength` attributes in HTML?

A) To improve user experience
B) To limit input size and prevent buffer overflow attacks
C) To increase page load speed
D) To reduce form submission time

✅ Answer: B) To limit input size and prevent buffer overflow attacks
Explanation: Limiting input size helps prevent buffer overflows and denial-of-service attacks.

66. What is a common attack vector for NoSQL injection?

A) JSON-based database queries
B) URL query parameters
C) HTML form fields
D) Email validation systems

✅ Answer: A) JSON-based database queries
Explanation: NoSQL injection exploits vulnerabilities in JSON query parsing, allowing attackers to manipulate queries.

67. Why is input validation critical in GraphQL APIs?

A) GraphQL allows deeply nested queries that can cause excessive server load
B) GraphQL is always secure by default
C) GraphQL does not process user input
D) GraphQL does not require input validation

✅ Answer: A) GraphQL allows deeply nested queries that can cause excessive server load
Explanation: Attackers can craft deep queries to perform DoS attacks if input validation is not enforced.

68. What is a primary security concern with auto-generated usernames?

A) Attackers can predict future usernames and gain unauthorized access
B) Users might not like their username
C) Auto-generated usernames are hard to remember
D) They cannot be changed

✅ Answer: A) Attackers can predict future usernames and gain unauthorized access
Explanation: Predictable usernames make brute-force attacks easier.

69. Why is `X-Content-Type-Options: nosniff` an important security header?

A) It prevents the browser from guessing content types, reducing XSS risks
B) It speeds up page load times
C) It blocks all JavaScript execution
D) It forces HTTPS

✅ Answer: A) It prevents the browser from guessing content types, reducing XSS risks
Explanation: This header prevents MIME-type sniffing, reducing security risks.

71. What is a key security flaw when accepting XML input without validation?

A) It slows down application performance
B) It can lead to XML External Entity (XXE) injection
C) It prevents users from submitting large files
D) It allows attackers to bypass authentication

✅ Answer: B) It can lead to XML External Entity (XXE) injection
Explanation: XXE injection occurs when an application parses XML without disabling external entity resolution, allowing attackers to read sensitive files or perform SSRF.

72. How can Regular Expression Denial of Service (ReDoS) be mitigated in input validation?

A) Using overly complex regex patterns
B) Limiting input length and using efficient regex patterns
C) Allowing only alphanumeric characters
D) Storing user input before validation

✅ Answer: B) Limiting input length and using efficient regex patterns
Explanation: Inefficient regex patterns can be exploited with crafted input to cause excessive processing time (ReDoS attack).

73. Which of the following security risks does improper input validation contribute to?

A) SQL Injection
B) Cross-Site Scripting (XSS)
C) Command Injection
D) All of the above

✅ Answer: D) All of the above
Explanation: Improper input validation is a root cause of many vulnerabilities, including SQLi, XSS, and command injection.

74. Why is input validation especially important in IoT devices?

A) IoT devices have limited storage
B) IoT devices often process untrusted input from multiple sources
C) IoT devices do not support advanced encryption
D) IoT devices do not require authentication

✅ Answer: B) IoT devices often process untrusted input from multiple sources
Explanation: Unvalidated input can allow attackers to manipulate IoT functionality, leading to exploits like remote command execution.

75. What security risk arises from allowing unrestricted Unicode characters in user input?

A) Attackers can exploit homoglyph attacks (e.g., domain spoofing)
B) It makes input processing faster
C) It improves user experience
D) Unicode characters are always safe

✅ Answer: A) Attackers can exploit homoglyph attacks (e.g., domain spoofing)
Explanation: Certain Unicode characters can mimic normal letters (e.g., “ρaypal.com” instead of “paypal.com”), leading to phishing attacks.

76. What is a primary reason for input sanitization before inserting data into a NoSQL database?

A) NoSQL databases do not support traditional SQL injection
B) Attackers can manipulate JSON input to perform injection attacks
C) NoSQL databases do not require authentication
D) NoSQL databases cannot be attacked

✅ Answer: B) Attackers can manipulate JSON input to perform injection attacks
Explanation: NoSQL injections exploit poorly validated JSON input to manipulate database queries.

77. What is a common flaw when using `filter_var()` for input validation in PHP?

A) It does not validate numeric values
B) It may allow certain unexpected input values
C) It does not work with server-side validation
D) It is only useful for client-side validation

✅ Answer: B) It may allow certain unexpected input values
Explanation: While filter_var() is useful, it is not foolproof and must be combined with strict input validation rules.

78. Why should HTML form inputs have `required` attributes in addition to server-side validation?

A) It prevents unnecessary requests to the server
B) It enhances client-side user experience but should not replace server-side validation
C) It replaces the need for server-side validation
D) It allows attackers to bypass validation

✅ Answer: B) It enhances client-side user experience but should not replace server-side validation
Explanation: The required attribute helps at the client level, but it can be bypassed, so server-side validation is always necessary.

79. What type of attack can occur if user input is directly used in an `eval()` function in Python?

A) Buffer Overflow
B) Remote Code Execution (RCE)
C) SQL Injection
D) Clickjacking

✅ Answer: B) Remote Code Execution (RCE)
Explanation: Using eval() with untrusted input can allow an attacker to execute arbitrary Python code.

80. Which HTTP header can help protect against reflected XSS attacks?

A) X-XSS-Protection: 1; mode=block
B) Strict-Transport-Security
C) Referrer-Policy
D) Content-Type

✅ Answer: A) X-XSS-Protection: 1; mode=block
Explanation: This header instructs browsers to block reflective XSS attacks if detected.

81. Why is using `parseInt(userInput)` in JavaScript without validation risky?

A) It can convert non-numeric values into numbers unexpectedly
B) It is slow
C) It does not work on all browsers
D) It allows cross-site scripting

✅ Answer: A) It can convert non-numeric values into numbers unexpectedly
Explanation: parseInt() may return unintended results if user input contains unexpected characters.

82. Why is it dangerous to allow users to enter URLs without validation?

A) URLs are difficult to store in databases
B) Users may enter incorrect URLs
C) Attackers can inject malicious redirects or SSRF payloads
D) URLs do not need validation

✅ Answer: C) Attackers can inject malicious redirects or SSRF payloads
Explanation: Unvalidated URLs can lead to open redirects, SSRF, and phishing attacks.

83. What is a common security misconfiguration when handling input in APIs?

A) Allowing API consumers to send JSON requests
B) Using strict schemas for input validation
C) Accepting unrestricted input and dynamically generating database queries
D) Using rate-limiting for API calls

✅ Answer: C) Accepting unrestricted input and dynamically generating database queries
Explanation: Unrestricted input can lead to NoSQL injection, SQL injection, or API abuse.

84. How does limiting user input length help prevent security risks?

A) It prevents buffer overflow and ReDoS attacks
B) It makes database storage more efficient
C) It improves user experience
D) It prevents users from submitting incorrect data

✅ Answer: A) It prevents buffer overflow and ReDoS attacks
Explanation: Restricting input length ensures that excessively large or malicious payloads cannot be processed.

85. What is the main benefit of Content Security Policy (CSP) in preventing XSS?

A) It blocks all JavaScript
B) It defines allowed sources of scripts, styles, and content
C) It replaces the need for input validation
D) It encrypts user input

✅ Answer: B) It defines allowed sources of scripts, styles, and content
Explanation: CSP limits where scripts can be loaded from, mitigating XSS risks.

86. What should be avoided when handling user-uploaded filenames?

A) Allowing filenames with special characters and spaces
B) Storing filenames as metadata
C) Renaming files before storage
D) Restricting allowed file extensions

✅ Answer: A) Allowing filenames with special characters and spaces
Explanation: Special characters in filenames can lead to path traversal and command injection attacks.

87. How can Cross-Site Script Inclusion (XSSI) be mitigated?

A) Using JSONP for cross-domain requests
B) Ensuring JSON responses are prefixed with )]}'
C) Allowing unrestricted cross-origin resource sharing (CORS)
D) Storing JSON responses in cookies

✅ Answer: B) Ensuring JSON responses are prefixed with )]}'
Explanation: Adding a prefix prevents browsers from parsing JSON as JavaScript.

91. Why is normalizing input before validation important?

A) It reduces the length of the input
B) It ensures input is consistent before applying validation rules
C) It converts input into a random string
D) It makes input validation unnecessary

✅ Answer: B) It ensures input is consistent before applying validation rules
Explanation: Normalizing input (e.g., trimming spaces, converting to lowercase) helps prevent inconsistencies that attackers might exploit.

92. What is a major security concern when processing XML input?

A) XML input is always large and slow to process
B) XML input can be manipulated to trigger XML External Entity (XXE) attacks
C) XML does not support validation
D) XML can only be used in REST APIs

✅ Answer: B) XML input can be manipulated to trigger XML External Entity (XXE) attacks
Explanation: Improper XML parsing can allow attackers to read files, initiate SSRF, or execute DoS attacks.

93. What is the purpose of validating HTTP request headers?

A) To ensure they contain correct capitalization
B) To prevent HTTP header injection attacks
C) To make the server run faster
D) To allow debugging of network requests

✅ Answer: B) To prevent HTTP header injection attacks
Explanation: Attackers can manipulate headers to perform request smuggling, cache poisoning, or other injection attacks.

94. Which type of attack exploits poorly validated redirects and forwards?

A) Cross-Site Scripting (XSS)
B) Open Redirect Attacks
C) Buffer Overflow
D) SQL Injection

✅ Answer: B) Open Redirect Attacks
Explanation: Unvalidated redirects allow attackers to redirect users to malicious websites, often used in phishing attacks.

95. What is a security risk of using client-side JavaScript for input validation only?

A) JavaScript validation makes web pages load slower
B) Users can bypass it by disabling JavaScript or modifying requests
C) JavaScript validation does not work on mobile devices
D) Input validation should only be done in the browser

✅ Answer: B) Users can bypass it by disabling JavaScript or modifying requests
Explanation: Attackers can manipulate requests directly, bypassing client-side validation. Server-side validation is necessary.

96. What security risk is associated with accepting user-provided file paths without validation?

A) Path Traversal Attacks
B) Slow file upload speeds
C) Inability to track uploaded files
D) Large storage consumption

✅ Answer: A) Path Traversal Attacks
Explanation: Unvalidated file paths can allow attackers to access system files outside the intended directory (../../etc/passwd).

97. How does enforcing Content-Type validation improve security?

A) It ensures input matches the expected MIME type
B) It increases website performance
C) It blocks all cross-site scripting (XSS) attacks
D) It prevents users from submitting long input

✅ Answer: A) It ensures input matches the expected MIME type
Explanation: Verifying the Content-Type header ensures that input matches expected data formats, preventing data manipulation.

98. What is the most secure way to handle JSON web tokens (JWTs) in user input?

A) Decode and validate JWT structure before using it
B) Accept any JWT from a user request
C) Store JWTs in cookies without restrictions
D) Allow users to modify their JWT manually

✅ Answer: A) Decode and validate JWT structure before using it
Explanation: JWTs should be validated for authenticity and integrity before being used in authentication or authorization.

99. What is the primary defense against CSV injection attacks?

A) Removing all numeric values from CSV input
B) Escaping values that begin with =, +, @, or - before saving
C) Converting CSV input to uppercase
D) Replacing all commas with spaces

✅ Answer: B) Escaping values that begin with =, +, @, or - before saving
Explanation: Certain spreadsheet formulas (=SUM(A1:A2)) can be executed when opening a CSV file, leading to CSV injection attacks.

100. Why should untrusted user input never be directly used in database queries?

A) It slows down database queries
B) It can lead to SQL injection attacks
C) It reduces database performance
D) It prevents users from inserting new records

✅ Answer: B) It can lead to SQL injection attacks
Explanation: Directly using user input in queries allows attackers to manipulate SQL statements, extract data, or gain unauthorized access.

101. Which of the following is a primary reason to enforce a maximum length on user input?

A) It prevents XSS attacks
B) It improves the efficiency of data storage
C) It helps prevent buffer overflow and denial-of-service (DoS) attacks
D) It ensures users enter only valid email addresses

✅ Answer: C) It helps prevent buffer overflow and denial-of-service (DoS) attacks
Explanation: Limiting input length prevents attackers from submitting excessively large payloads that could cause memory overflows or DoS attacks.

102. What is a major risk when allowing users to input JavaScript code?

A) It can cause the website to crash
B) It increases the load time of the webpage
C) It can lead to Cross-Site Scripting (XSS) attacks
D) It makes debugging more difficult

✅ Answer: C) It can lead to Cross-Site Scripting (XSS) attacks
Explanation: Allowing JavaScript input without sanitization can enable attackers to inject and execute malicious scripts.

103. Which security measure helps prevent HTTP parameter pollution attacks?

A) Removing duplicate parameters from requests
B) Allowing multiple parameters with the same name
C) Encoding all request parameters
D) Converting input values to lowercase

✅ Answer: A) Removing duplicate parameters from requests
Explanation: HTTP parameter pollution occurs when attackers manipulate duplicate parameters to bypass validation or modify server behavior.

104. Why should applications restrict the use of special characters in input fields?

A) Special characters slow down database queries
B) Special characters can be used for injection attacks
C) Special characters are difficult for users to type
D) Special characters increase network latency

✅ Answer: B) Special characters can be used for injection attacks
Explanation: Attackers use special characters like ', ", <, >, and ; to craft injection attacks in SQL, XSS, and command injection.

105. What is the risk of allowing unrestricted user-generated HTML input?

A) It increases page load time
B) It can lead to stored XSS attacks
C) It prevents browser caching
D) It makes HTML pages harder to read

✅ Answer: B) It can lead to stored XSS attacks
Explanation: Stored XSS occurs when malicious HTML/JavaScript is saved in the database and executed when viewed by other users.

106. Why should file extensions be validated during file uploads?

A) To ensure files are properly named
B) To prevent execution of malicious files on the server
C) To speed up file processing
D) To allow only image uploads

✅ Answer: B) To prevent execution of malicious files on the server
Explanation: Attackers may upload files with dangerous extensions (.php, .exe, .sh) to execute arbitrary code on the server.

107. How does improper input validation affect logging mechanisms?

A) It prevents logs from storing error messages
B) It allows log injection attacks
C) It improves log readability
D) It reduces log storage space

✅ Answer: B) It allows log injection attacks
Explanation: Attackers can insert fake log entries or manipulate logs by injecting malicious input, hiding their activities.

108. What type of attack can occur if user input is directly used in OS commands?

A) Command Injection
B) SQL Injection
C) Cross-Site Scripting (XSS)
D) XML Injection

✅ Answer: A) Command Injection
Explanation: Command Injection occurs when attackers manipulate input to execute arbitrary commands on the system.

109. How can XML injection attacks be prevented?

A) By escaping all XML input
B) By disabling XML External Entity (XXE) processing
C) By converting XML to JSON
D) By allowing users to edit XML directly

✅ Answer: B) By disabling XML External Entity (XXE) processing
Explanation: XXE attacks occur when external entity resolution is enabled, allowing attackers to access local files or perform SSRF attacks.

110. Which validation approach should be taken when handling currency values?

A) Accept only numbers and a decimal point
B) Allow any alphanumeric input
C) Convert input to uppercase before processing
D) Store currency values as strings

✅ Answer: A) Accept only numbers and a decimal point
Explanation: Limiting currency input to numbers and decimals prevents injection attacks and ensures accurate processing.

111. What is the purpose of output encoding?

A) It encrypts user data before storage
B) It ensures user input is displayed as text rather than executable code
C) It increases website performance
D) It prevents unauthorized database access

✅ Answer: B) It ensures user input is displayed as text rather than executable code
Explanation: Encoding special characters prevents XSS by ensuring input is treated as text instead of code.

112. What is an effective way to prevent integer overflow vulnerabilities?

A) Limiting input length
B) Checking input type and range before processing
C) Allowing only positive numbers
D) Encoding integers before storing them

✅ Answer: B) Checking input type and range before processing
Explanation: Integer overflow occurs when a value exceeds the maximum storage limit. Validating the range prevents this.

113. What is a major risk of allowing unrestricted email addresses as input?

A) Users may enter incorrect email addresses
B) Attackers may exploit unvalidated input for email header injection
C) It slows down email processing
D) It prevents emails from being stored in the database

✅ Answer: B) Attackers may exploit unvalidated input for email header injection
Explanation: Email header injection allows attackers to manipulate email fields, leading to spam or phishing attacks.

114. Why should session identifiers not be accepted as user input?

A) They can be stored in local storage
B) They are unique to each user
C) They can be manipulated for session hijacking
D) They do not require validation

✅ Answer: C) They can be manipulated for session hijacking
Explanation: Attackers can modify session tokens to impersonate users or gain unauthorized access.

115. How does input validation help prevent Cross-Site Request Forgery (CSRF)?

A) It prevents users from submitting forms
B) It ensures input comes from an authenticated request
C) It encrypts all form submissions
D) It stores input in a secure format

✅ Answer: B) It ensures input comes from an authenticated request
Explanation: Validating input with CSRF tokens ensures that requests are legitimate and not forged by an attacker.

116. What is a security risk of allowing user-generated URLs without validation?

A) Attackers can redirect users to malicious websites
B) URLs are difficult to parse
C) URLs take up too much storage space
D) URLs do not require validation

✅ Answer: A) Attackers can redirect users to malicious websites
Explanation: Unvalidated URLs can lead to phishing attacks and malware distribution.

117. Why should web applications avoid auto-executing file downloads?

A) It increases server load
B) It allows attackers to deliver malware via drive-by downloads
C) Users may download duplicate files
D) File downloads should always be encrypted

✅ Answer: B) It allows attackers to deliver malware via drive-by downloads
Explanation: Malicious actors use auto-downloads to install malware without user interaction.

118. What security risk does unvalidated GraphQL queries introduce?

A) Query Injection Attacks
B) Buffer Overflow
C) Cross-Site Scripting (XSS)
D) Open Redirects

✅ Answer: A) Query Injection Attacks
Explanation: GraphQL query injections manipulate queries to extract unauthorized data.

121. Why should user input never be concatenated directly into SQL queries?

A) It makes queries run slower
B) It can lead to SQL Injection attacks
C) It increases the database storage size
D) It prevents users from entering long inputs

✅ Answer: B) It can lead to SQL Injection attacks
Explanation: Concatenating user input into SQL queries makes it possible for attackers to inject malicious SQL code.

122. Which of the following input validation techniques should be used for user-generated filenames?

A) Allow only alphanumeric characters and limited special characters
B) Allow users to name files freely without restrictions
C) Replace spaces with underscores but allow all special characters
D) Convert all filenames to uppercase

✅ Answer: A) Allow only alphanumeric characters and limited special characters
Explanation: Restricting filenames prevents directory traversal and command injection attacks.

123. How can applications prevent HTTP response splitting attacks?

A) Use TLS encryption
B) Sanitize newline characters in user input
C) Allow multiple headers in HTTP responses
D) Encode HTML output

✅ Answer: B) Sanitize newline characters in user input
Explanation: HTTP response splitting occurs when unsanitized user input manipulates HTTP headers, leading to security vulnerabilities.

124. What is a security risk of storing user input in cookies without validation?

A) Cookies can be manipulated to store malicious data
B) Cookies expire too quickly
C) Cookies do not support special characters
D) Cookies slow down browser performance

✅ Answer: A) Cookies can be manipulated to store malicious data
Explanation: Attackers can modify cookies to inject harmful data into web applications.

125. What is the primary defense against Host Header Injection attacks?

A) Accept user-supplied host headers without validation
B) Restrict accepted host headers to predefined values
C) Allow all host headers but log them
D) Convert host headers to lowercase

✅ Answer: B) Restrict accepted host headers to predefined values
Explanation: Host Header Injection can lead to cache poisoning, password reset poisoning, and SSRF.

126. What type of attack can occur if JSON input is not validated properly?

A) SQL Injection
B) JSON Injection
C) Cross-Site Scripting (XSS)
D) XML External Entity (XXE) Injection

✅ Answer: B) JSON Injection
Explanation: Attackers can manipulate JSON input to execute unexpected actions in web applications.

127. How does input validation protect against phishing attacks?

A) By checking that user input contains no special characters
B) By blocking links in user-generated content
C) By verifying that URLs belong to trusted domains
D) By limiting input length

✅ Answer: C) By verifying that URLs belong to trusted domains
Explanation: Validating URLs helps prevent attackers from embedding malicious links in input fields.

128. What is the primary purpose of an allowlist (whitelist) in input validation?

A) To block specific malicious input patterns
B) To allow only predefined, expected input formats
C) To store valid inputs in a database
D) To remove invalid characters from input

✅ Answer: B) To allow only predefined, expected input formats
Explanation: An allowlist ensures that only known, safe input values are accepted.

129. How does improper input validation impact session management?

A) It allows users to log in without credentials
B) It can lead to session fixation or session hijacking
C) It prevents session expiration
D) It blocks user access to valid sessions

✅ Answer: B) It can lead to session fixation or session hijacking
Explanation: Attackers can manipulate session tokens through poorly validated input, leading to session hijacking.

130. Why is it important to validate and sanitize input in GraphQL APIs?

A) GraphQL does not support authentication
B) GraphQL queries can be deeply nested and cause excessive resource consumption
C) GraphQL automatically prevents injection attacks
D) GraphQL does not require validation

✅ Answer: B) GraphQL queries can be deeply nested and cause excessive resource consumption
Explanation: GraphQL allows highly nested queries, which can be exploited to overload the server.

131. How does HTML attribute escaping prevent XSS attacks?

A) It replaces dangerous characters with safe alternatives
B) It encrypts all user input before rendering
C) It converts all user input to uppercase
D) It blocks JavaScript execution

✅ Answer: A) It replaces dangerous characters with safe alternatives
Explanation: Escaping ensures that user input is displayed as text rather than interpreted as HTML or JavaScript.

132. What is the purpose of restricting input in command-line arguments?

A) To improve command execution speed
B) To prevent Command Injection attacks
C) To make commands more readable
D) To reduce memory usage

✅ Answer: B) To prevent Command Injection attacks
Explanation: Command Injection occurs when unvalidated input is used in system commands.

133. What is a risk of allowing unrestricted user comments in a web application?

A) Users may submit duplicate comments
B) Attackers can inject malicious JavaScript (Stored XSS)
C) Users may enter long comments
D) Comments will take up too much storage

✅ Answer: B) Attackers can inject malicious JavaScript (Stored XSS)
Explanation: Stored XSS occurs when malicious scripts are stored in a database and executed when users view comments.

134. Why should web applications avoid displaying raw user input in error messages?

A) It makes error messages harder to read
B) It can reveal sensitive data and lead to information disclosure attacks
C) It reduces debugging efficiency
D) It slows down the application

✅ Answer: B) It can reveal sensitive data and lead to information disclosure attacks
Explanation: Error messages that display raw input can help attackers identify security vulnerabilities.

135. What is a security concern when using `eval()` to process user input in JavaScript?

A) It can slow down JavaScript execution
B) It can execute arbitrary code, leading to Remote Code Execution (RCE)
C) It prevents user input validation
D) It increases memory usage

✅ Answer: B) It can execute arbitrary code, leading to Remote Code Execution (RCE)
Explanation: eval() should never be used with user input because it can execute any JavaScript code.

136. How can applications prevent HTTP method tampering attacks?

A) By allowing users to specify their own HTTP methods
B) By enforcing strict access control rules on HTTP methods
C) By using only GET and POST methods
D) By blocking all user input

✅ Answer: B) By enforcing strict access control rules on HTTP methods
Explanation: Attackers may attempt to use unsupported HTTP methods to bypass security controls.

137. What is a major security risk of allowing user-controlled input in API endpoints?

A) Users may send too many requests
B) Attackers may exploit unvalidated input for API injection attacks
C) Users may enter incorrect data
D) API performance may decrease

✅ Answer: B) Attackers may exploit unvalidated input for API injection attacks
Explanation: Poorly validated input can lead to API injection vulnerabilities, compromising security.

138. Why should input validation be performed before storing data in a database?

A) To reduce the size of the database
B) To prevent injection attacks and maintain data integrity
C) To improve query performance
D) To allow faster data retrieval

✅ Answer: B) To prevent injection attacks and maintain data integrity
Explanation: Validating input before storage prevents SQL injection and ensures database integrity.

139. What is an effective mitigation for LDAP Injection attacks?

A) Using parameterized LDAP queries
B) Allowing unrestricted LDAP queries
C) Logging all LDAP queries
D) Accepting only lowercase input in LDAP queries

✅ Answer: A) Using parameterized LDAP queries
Explanation: Parameterized LDAP queries prevent user input from being interpreted as part of the LDAP query.

121. Why should developers validate file MIME types in addition to file extensions?

A) File extensions alone do not determine a file’s actual content type
B) It reduces server load
C) It speeds up file uploads
D) File extensions are case-sensitive

✅ Answer: A) File extensions alone do not determine a file’s actual content type
Explanation: Attackers can rename malicious files (e.g., .exe to .jpg), but MIME type validation ensures correct content handling.

122. What security risk arises when an application automatically decodes user input?

A) It slows down input processing
B) It allows attackers to encode payloads to bypass validation
C) It makes input validation easier
D) It prevents SQL Injection attacks

✅ Answer: B) It allows attackers to encode payloads to bypass validation
Explanation: Automatic decoding can allow attackers to obfuscate malicious input, bypassing security filters.

123. Which of the following is NOT an effective way to sanitize user input?

A) Using parameterized queries
B) Escaping output before rendering
C) Stripping all numeric values
D) Whitelist-based validation

✅ Answer: C) Stripping all numeric values
Explanation: Removing numbers does not provide security; proper validation techniques like whitelisting and escaping are more effective.

124. Why should applications reject input containing null bytes (`%00`)?

A) Null bytes can be used to terminate strings prematurely and bypass security filters
B) Null bytes slow down input processing
C) Null bytes are required for SQL Injection attacks
D) Null bytes increase database storage space

✅ Answer: A) Null bytes can be used to terminate strings prematurely and bypass security filters
Explanation: Attackers use null byte injection to manipulate input processing, often bypassing security filters.

125. What is a major risk when user input is used in dynamically generated JSON responses?

A) JSON processing is slow
B) JSONP hijacking or Cross-Site Script Inclusion (XSSI) attacks
C) JSON does not support security features
D) JSON is difficult to parse

✅ Answer: B) JSONP hijacking or Cross-Site Script Inclusion (XSSI) attacks
Explanation: Unvalidated JSON responses can be exploited to steal sensitive data if exposed to external scripts.

126. How can developers prevent directory traversal attacks?

A) Encode user input before storing
B) Restrict file path inputs and use an allowlist
C) Convert all file paths to uppercase
D) Replace all / and \ with underscores

✅ Answer: B) Restrict file path inputs and use an allowlist
Explanation: Attackers use directory traversal (../../etc/passwd) to access unauthorized files, so paths should be strictly validated.

127. What is a common mistake in input validation for CAPTCHA systems?

A) Allowing CAPTCHAs to be case-sensitive
B) Using predictable CAPTCHA values
C) Using image-based CAPTCHAs
D) Storing CAPTCHA responses in a session

✅ Answer: B) Using predictable CAPTCHA values
Explanation: If CAPTCHA responses follow a predictable pattern, bots can easily bypass them.

128. What is a major security risk of using `innerHTML` in JavaScript?

A) It can allow XSS if user input is inserted directly
B) It makes JavaScript slower
C) It does not support modern browsers
D) It requires additional libraries to function

✅ Answer: A) It can allow XSS if user input is inserted directly
Explanation: innerHTML executes HTML and JavaScript, making it vulnerable to XSS if not properly sanitized.

129. What type of validation should be used for phone number input fields?

A) Accept only numeric characters and limit length
B) Convert all input to lowercase
C) Allow any alphanumeric characters
D) Store phone numbers as integers in the database

✅ Answer: A) Accept only numeric characters and limit length
Explanation: Restricting phone number input to numbers and setting length limits prevents injection attacks.

130. How can email header injection be prevented?

A) Restricting newline characters (\n, \r) in email fields
B) Converting all emails to lowercase
C) Storing emails in JSON format
D) Encrypting all email addresses

✅ Answer: A) Restricting newline characters (\n, \r) in email fields
Explanation: Attackers use newlines in email headers to inject additional recipients or content, leading to spam attacks.

131. What is a security risk of accepting XML input without schema validation?

A) XML data cannot be formatted correctly
B) It allows injection attacks, such as XXE and XML bombs
C) XML input is always safe
D) Schema validation is only required for JSON

✅ Answer: B) It allows injection attacks, such as XXE and XML bombs
Explanation: Unvalidated XML input can lead to XXE attacks (leaking sensitive files) and billion laughs attacks (denial-of-service via nested XML entities).

132. How can Cross-Origin Resource Sharing (CORS) misconfiguration lead to security risks?

A) It allows attackers to bypass input validation
B) It prevents requests from being made across different domains
C) It enables unauthorized access to sensitive API data
D) It causes JavaScript errors

✅ Answer: C) It enables unauthorized access to sensitive API data
Explanation: Overly permissive CORS settings (Access-Control-Allow-Origin: *) allow attackers to make unauthorized cross-origin requests.

133. What is a secure way to handle user-generated filenames?

A) Store the original filename
B) Use a randomized filename and restrict special characters
C) Allow users to choose filenames with any characters
D) Convert filenames to lowercase before storing

✅ Answer: B) Use a randomized filename and restrict special characters
Explanation: Attackers can use special filenames to execute attacks (e.g., ../../shell.php), so filenames should be randomized and sanitized.

134. Why should developers avoid using `eval()` with user input?

A) It causes performance issues
B) It can execute arbitrary code, leading to Remote Code Execution (RCE)
C) It makes debugging difficult
D) It does not work in all browsers

✅ Answer: B) It can execute arbitrary code, leading to Remote Code Execution (RCE)
Explanation: eval() should never be used with user input as it allows attackers to execute malicious code.

135. What is the risk of allowing unrestricted redirects in a web application?

A) It allows Open Redirect attacks
B) It makes the application slower
C) It prevents caching of redirects
D) It improves user experience

✅ Answer: A) It allows Open Redirect attacks
Explanation: Open redirects can be abused in phishing attacks to trick users into visiting malicious sites.

136. How can developers mitigate Host Header Injection attacks?

A) Validate the Host header against a predefined allowlist
B) Allow any host header value
C) Remove the Host header from all requests
D) Convert hostnames to lowercase

✅ Answer: A) Validate the Host header against a predefined allowlist
Explanation: Restricting allowed hostnames prevents attackers from injecting malicious headers.

137. What is a security risk when processing user-generated CSV files?

A) Spreadsheet Formula Injection
B) JSON Injection
C) Open Redirects
D) MIME Type Spoofing

✅ Answer: A) Spreadsheet Formula Injection
Explanation: Malicious formulas (=SUM(A1:A2), =cmd|' /C calc'!A0) in CSV files can execute when opened in spreadsheet software.

138. What is an important security measure when handling URL query parameters?

A) Always encode user input before including it in a URL
B) Convert all query parameters to uppercase
C) Remove all numeric values from query parameters
D) Allow unrestricted URL parameters

✅ Answer: A) Always encode user input before including it in a URL
Explanation: Encoding prevents injection attacks like SQLi, XSS, and HTTP header manipulation.

139. Why should applications reject excessively complex regular expressions in input validation?

A) They slow down the application and may lead to Regular Expression Denial of Service (ReDoS)
B) They improve security by allowing more flexibility
C) They make the application easier to debug
D) They prevent Cross-Site Scripting (XSS)

✅ Answer: A) They slow down the application and may lead to Regular Expression Denial of Service (ReDoS)
Explanation: Poorly written regex patterns can be exploited to cause excessive backtracking, resulting in DoS attacks.

140. What is a primary defense mechanism against WebSockets injection attacks?

A) Validate and sanitize all WebSocket messages
B) Allow all input but log unexpected messages
C) Encode all input as base64 before processing
D) Use only WebSockets over HTTP

✅ Answer: A) Validate and sanitize all WebSocket messages
Explanation: Attackers can manipulate WebSocket messages to inject malicious payloads, so strict validation is necessary.

141. How does improper input validation contribute to Account Takeover (ATO) attacks?

A) It allows attackers to inject SQL queries
B) It enables attackers to bypass authentication checks by injecting unexpected values
C) It prevents brute-force attempts
D) It causes password hashing to fail

✅ Answer: B) It enables attackers to bypass authentication checks by injecting unexpected values
Explanation: Poor input validation in authentication fields can lead to ATO through bypass techniques.

142. Why should applications restrict input in API request bodies?

A) To prevent users from sending long messages
B) To mitigate API Injection and Mass Assignment attacks
C) To improve server response times
D) To store API requests efficiently

✅ Answer: B) To mitigate API Injection and Mass Assignment attacks
Explanation: Allowing unrestricted input in APIs can enable attackers to manipulate object properties and exploit vulnerabilities.

143. What is a risk of allowing users to submit raw HTML in form inputs?

A) It increases the size of the database
B) It can lead to Stored Cross-Site Scripting (XSS) attacks
C) It improves page load speed
D) It makes form validation unnecessary

✅ Answer: B) It can lead to Stored Cross-Site Scripting (XSS) attacks
Explanation: Allowing raw HTML without sanitization enables attackers to inject malicious scripts into stored content.

144. How can developers prevent HTTP Verb Tampering attacks?

A) Restrict allowed HTTP methods and enforce proper authentication checks
B) Convert all HTTP requests to GET
C) Allow users to modify HTTP methods
D) Log all HTTP requests but do not block them

✅ Answer: A) Restrict allowed HTTP methods and enforce proper authentication checks
Explanation: Attackers may alter HTTP methods (POST to DELETE) to bypass security controls, so strict method validation is essential.

145. What is an effective way to prevent cache poisoning attacks via input validation?

A) Restrict untrusted input in HTTP headers, especially Host and Referer
B) Allow all inputs but log unexpected values
C) Convert all user input to lowercase before caching
D) Disable caching for all pages

✅ Answer: A) Restrict untrusted input in HTTP headers, especially Host and Referer
Explanation: Attackers manipulate cache-related headers to serve malicious content, so filtering these inputs prevents poisoning.

146. Why is it important to validate input used in dynamic DNS lookups?

A) To prevent Domain Name System (DNS) Rebinding attacks
B) To ensure DNS queries return valid results
C) To reduce network latency
D) To improve DNS caching

✅ Answer: A) To prevent Domain Name System (DNS) Rebinding attacks
Explanation: Unvalidated DNS queries can be used to manipulate domain resolutions and bypass Same-Origin Policy (SOP).

147. What type of validation should be enforced for user-submitted URL inputs?

A) Use allowlist validation and verify URL formatting
B) Accept all URL formats and store them as text
C) Convert URLs to IP addresses before storing
D) Remove all special characters from the URL

✅ Answer: A) Use allowlist validation and verify URL formatting
Explanation: Allowlisting valid domains and verifying URL structures prevent malicious redirects and SSRF attacks.

148. How does strict input validation prevent Server-Side Request Forgery (SSRF)?

A) It blocks users from making requests to internal or restricted resources
B) It prevents users from submitting forms
C) It encrypts all request data
D) It limits the length of URLs

✅ Answer: A) It blocks users from making requests to internal or restricted resources
Explanation: SSRF exploits occur when attackers manipulate server-side requests, so input validation should prevent internal URL access.

149. What is a common mistake when implementing CAPTCHA validation?

A) Using a static CAPTCHA that does not change
B) Allowing CAPTCHAs on login pages
C) Using image-based CAPTCHAs
D) Storing CAPTCHA responses in a session

✅ Answer: A) Using a static CAPTCHA that does not change
Explanation: Static CAPTCHAs are predictable and can be easily bypassed by automated bots.

150. What is a security risk of allowing input in system log messages?

A) It can lead to Log Injection or Log Forgery attacks
B) It increases log file size
C) It slows down logging processes
D) It makes logs harder to read

✅ Answer: A) It can lead to Log Injection or Log Forgery attacks
Explanation: Attackers can inject false log entries or manipulate logs to hide their activities, leading to forensic challenges.

151. What is the security risk of allowing unrestricted Unicode characters in input fields?

A) Attackers can use homoglyphs to disguise malicious input
B) It makes input validation easier
C) It prevents SQL injection
D) It reduces the risk of buffer overflows

✅ Answer: A) Attackers can use homoglyphs to disguise malicious input
Explanation: Certain Unicode characters visually resemble normal letters (e.g., Cyrillic “а” instead of Latin “a”), allowing attackers to disguise phishing URLs or bypass security filters.

152. How can excessive input nesting in XML data be exploited?

A) It can cause XML External Entity (XXE) attacks
B) It can lead to a “billion laughs” attack, causing a denial of service
C) It can increase data storage costs
D) It can prevent SQL injection

✅ Answer: B) It can lead to a “billion laughs” attack, causing a denial of service
Explanation: Deeply nested XML can be used to trigger exponential entity expansion, consuming excessive system resources.

153. How can user-controlled input in SQL `ORDER BY` clauses be exploited?

A) It can be used to modify database queries for enumeration attacks
B) It prevents SQL injection
C) It enhances query performance
D) It limits the number of results returned

✅ Answer: A) It can be used to modify database queries for enumeration attacks
Explanation: Allowing user-controlled ORDER BY input can let attackers enumerate database column names and optimize attack vectors.

**154. What is a major risk of allowing wildcard (`*`) input in database queries?**

A) It can lead to excessive data exposure
B) It speeds up database queries
C) It prevents SQL injection
D) It prevents unauthorized data access

✅ Answer: A) It can lead to excessive data exposure
Explanation: Using SELECT * without restriction can expose sensitive data if an attacker manipulates query conditions.

155. Why should input validation be applied to JSON web token (JWT) claims?

A) To prevent attackers from injecting malicious data into token claims
B) To make tokens expire faster
C) To increase JWT signature length
D) To store JWTs in local storage

✅ Answer: A) To prevent attackers from injecting malicious data into token claims
Explanation: JWT claims should be validated to ensure they contain only expected values, preventing privilege escalation attacks.

156. How can improper handling of user input in log files lead to security risks?

A) Attackers can inject control characters to manipulate log file output
B) It increases log file storage costs
C) It makes log entries harder to read
D) It speeds up logging performance

✅ Answer: A) Attackers can inject control characters to manipulate log file output
Explanation: Log injection attacks allow attackers to insert misleading or malicious data into log files, hiding malicious activity.

157. Why should applications avoid reflecting user input in HTTP error messages?

A) It can expose sensitive system details and enable information disclosure attacks
B) It improves user experience
C) It helps debug application errors faster
D) It prevents injection attacks

✅ Answer: A) It can expose sensitive system details and enable information disclosure attacks
Explanation: Reflecting raw user input in error messages can help attackers identify security weaknesses in an application.

158. What type of attack can occur if user-controlled input is used to generate filenames?

A) Path Traversal Attacks
B) Clickjacking
C) SQL Injection
D) Open Redirect Attacks

✅ Answer: A) Path Traversal Attacks
Explanation: Unvalidated filenames can be manipulated to access sensitive files outside of the intended directory.

159. Why should input length validation be enforced for numeric fields?

A) To prevent integer overflow attacks
B) To speed up calculations
C) To improve user experience
D) To ensure database storage efficiency

✅ Answer: A) To prevent integer overflow attacks
Explanation: Integer overflows occur when excessively large numbers exceed system limits, leading to unexpected behavior or security vulnerabilities.

160. What is a common risk when using `stripslashes()` for input sanitization in PHP?

A) It can be bypassed by attackers using different encoding techniques
B) It removes all special characters from input
C) It ensures secure database queries
D) It automatically prevents SQL injection

✅ Answer: A) It can be bypassed by attackers using different encoding techniques
Explanation: stripslashes() only removes backslashes, but attackers can use alternative encoding methods to bypass sanitization.

161. How can API endpoints be protected from input-based attacks?

A) Validate request parameters and enforce rate-limiting
B) Allow unrestricted user input
C) Only accept GET requests
D) Log all API requests without validation

✅ Answer: A) Validate request parameters and enforce rate-limiting
Explanation: Validating API input prevents injection attacks, while rate-limiting mitigates brute-force and DoS attacks.

162. Why is it important to validate user input in search queries?

A) To prevent SQL Injection and Denial of Service (DoS) attacks
B) To improve search engine indexing
C) To reduce query execution time
D) To allow all input types

✅ Answer: A) To prevent SQL Injection and Denial of Service (DoS) attacks
Explanation: Search queries can be exploited for SQL Injection or crafted to overload the database, causing DoS.

163. How can developers prevent HTTP request smuggling attacks?

A) Normalize and validate HTTP headers before processing
B) Allow unrestricted headers in HTTP requests
C) Convert all HTTP headers to lowercase
D) Encode all HTTP requests

✅ Answer: A) Normalize and validate HTTP headers before processing
Explanation: Request smuggling exploits inconsistencies in HTTP processing, so normalizing headers helps prevent manipulation.

164. What is a key security measure to prevent template injection attacks?

A) Disable dynamic template rendering for untrusted input
B) Allow users to modify templates freely
C) Store template files in a public directory
D) Encode template output as JSON

✅ Answer: A) Disable dynamic template rendering for untrusted input
Explanation: Template injection allows attackers to execute arbitrary code if user input is rendered dynamically.

165. Why should web applications sanitize input before storing it in a database?

A) To prevent SQL Injection and Stored XSS attacks
B) To increase database performance
C) To compress user input
D) To prevent data loss

✅ Answer: A) To prevent SQL Injection and Stored XSS attacks
Explanation: Sanitizing input ensures malicious payloads are not stored and later executed.

166. What is a common risk when using untrusted input in `eval()` functions in Python?

A) Remote Code Execution (RCE)
B) JSON Injection
C) SQL Injection
D) Open Redirects

✅ Answer: A) Remote Code Execution (RCE)
Explanation: Using eval() with unvalidated input allows attackers to execute arbitrary Python code.

167. Why is it dangerous to store unvalidated user input in session variables?

A) Attackers can manipulate session data for privilege escalation
B) It increases memory usage
C) It prevents session expiration
D) It slows down authentication

✅ Answer: A) Attackers can manipulate session data for privilege escalation
Explanation: Storing unvalidated input in sessions can allow attackers to modify session values and escalate privileges.

168. How can developers prevent file inclusion vulnerabilities?

A) Restrict file paths and use allowlist validation
B) Allow users to include any file
C) Accept all file types without restrictions
D) Convert all file paths to uppercase

✅ Answer: A) Restrict file paths and use allowlist validation
Explanation: File inclusion vulnerabilities allow attackers to execute unauthorized files, so strict path validation is necessary.

171. What is a major risk of allowing input in `Referer` headers without validation?

A) Attackers can manipulate the Referer header for CSRF attacks
B) It slows down website performance
C) It prevents XSS attacks
D) It makes logging more accurate

✅ Answer: A) Attackers can manipulate the Referer header for CSRF attacks
Explanation: Unvalidated Referer headers can be altered to forge requests and bypass security measures in CSRF attacks.

172. Why should API endpoints reject unexpected HTTP methods?

A) To prevent HTTP method manipulation attacks
B) To improve API performance
C) To allow dynamic routing
D) To reduce server load

✅ Answer: A) To prevent HTTP method manipulation attacks
Explanation: Restricting allowed HTTP methods prevents attackers from performing unauthorized actions via method tampering.

173. What is a security risk of using `.htaccess` files to filter input validation rules?

A) .htaccess rules can be bypassed using alternate encoding methods
B) .htaccess files improve performance
C) .htaccess files do not affect security
D) Input validation should only be performed at the browser level

✅ Answer: A) .htaccess rules can be bypassed using alternate encoding methods
Explanation: Attackers can encode input in unexpected ways (e.g., URL encoding) to bypass server-level security rules.

174. What is the risk of allowing unrestricted characters in password fields?

A) It increases the likelihood of password cracking attacks
B) It makes passwords stronger
C) It prevents SQL injection
D) It improves user experience

✅ Answer: A) It increases the likelihood of password cracking attacks
Explanation: Allowing unrestricted characters can enable attacks like null byte injection or hash manipulation. Strong password policies should be enforced.

175. How can developers prevent Open Graph injection attacks?

A) Validate and sanitize all metadata input fields
B) Disable caching for Open Graph data
C) Allow unrestricted Open Graph metadata input
D) Store Open Graph metadata in session variables

✅ Answer: A) Validate and sanitize all metadata input fields
Explanation: Attackers can manipulate Open Graph tags to alter link previews, leading to phishing or misinformation attacks.

176. Why should applications reject user-generated filenames containing spaces?

A) Spaces can be used in command injection attacks
B) Spaces slow down file processing
C) Spaces prevent filenames from being displayed correctly
D) Spaces increase storage costs

✅ Answer: A) Spaces can be used in command injection attacks
Explanation: Attackers can exploit spaces in filenames to execute commands (rm -rf file .txt).

177. What is the purpose of enforcing schema validation on JSON input?

A) To prevent JSON Injection attacks
B) To allow flexible input structures
C) To speed up API response times
D) To improve UI rendering

✅ Answer: A) To prevent JSON Injection attacks
Explanation: Schema validation ensures only expected fields are processed, preventing injection attacks.

178. Why should input from browser autofill features be validated?

A) Attackers can manipulate autofill data to insert malicious input
B) Autofill data is always trusted
C) Autofill speeds up user input
D) Autofill data is always encrypted

✅ Answer: A) Attackers can manipulate autofill data to insert malicious input
Explanation: Autofill features can be exploited to inject unauthorized data into web forms.

179. What type of attack can occur if an application logs user input without sanitization?

A) Log Injection
B) SQL Injection
C) DNS Spoofing
D) Clickjacking

✅ Answer: A) Log Injection
Explanation: Attackers can insert special characters in logs to manipulate log entries, forge actions, or execute malicious commands.

180. How can developers prevent request forgery attacks on internal applications?

A) Validate input using allowlists and restrict internal API access
B) Allow all API requests to be processed without validation
C) Convert all internal requests to uppercase
D) Accept only JSON input

✅ Answer: A) Validate input using allowlists and restrict internal API access
Explanation: Restricting internal request parameters prevents attackers from forging requests to manipulate internal services.

181. What is a major risk of allowing user-controlled HTTP headers?

A) HTTP header injection attacks
B) Increased network latency
C) Cross-Site Scripting (XSS)
D) Faster response times

✅ Answer: A) HTTP header injection attacks
Explanation: Unvalidated headers can be exploited to inject malicious content, leading to security vulnerabilities.

182. Why should form action URLs be validated in web applications?

A) To prevent form redirection attacks
B) To improve form submission speed
C) To allow cross-domain requests
D) To make forms easier to use

✅ Answer: A) To prevent form redirection attacks
Explanation: Attackers can manipulate form actions to redirect users to malicious websites.

183. How can applications prevent Host Header Poisoning attacks?

A) Restrict valid hostnames and reject untrusted headers
B) Convert all headers to lowercase
C) Allow all host headers but log them
D) Remove the Host header from requests

✅ Answer: A) Restrict valid hostnames and reject untrusted headers
Explanation: Attackers can manipulate host headers to redirect users to fake sites or exploit internal services.

184. Why is it dangerous to allow newline characters (`\n`, `\r`) in input fields?

A) They can be used in HTTP header and log injection attacks
B) They make user input harder to read
C) They increase the size of input fields
D) They slow down form submissions

✅ Answer: A) They can be used in HTTP header and log injection attacks
Explanation: Newline characters can manipulate headers or logs, leading to injection vulnerabilities.

185. What is the main risk of allowing dynamic database table names in user input?

A) SQL Injection attacks
B) Increased database performance
C) Slower database queries
D) Inability to log database changes

✅ Answer: A) SQL Injection attacks
Explanation: Attackers can manipulate dynamic table names to gain unauthorized access to data.

186. How does input validation help prevent Business Logic Vulnerabilities?

A) By ensuring that input follows expected workflows and constraints
B) By blocking all special characters
C) By allowing only numeric input
D) By logging all input

✅ Answer: A) By ensuring that input follows expected workflows and constraints
Explanation: Business logic vulnerabilities occur when attackers exploit weak application workflows.

187. Why should CAPTCHA systems include input validation?

A) To prevent automated bots from bypassing security measures
B) To make CAPTCHA images more readable
C) To improve page loading speed
D) To allow only uppercase responses

✅ Answer: A) To prevent automated bots from bypassing security measures
Explanation: Validating CAPTCHA input ensures that it is processed correctly and prevents automated bypass techniques.

188. How can developers prevent WebSocket hijacking attacks?

A) Validate WebSocket messages and enforce authentication tokens
B) Allow all WebSocket connections without validation
C) Disable WebSockets in web applications
D) Convert WebSocket messages to plain text

✅ Answer: A) Validate WebSocket messages and enforce authentication tokens
Explanation: Attackers can intercept WebSocket connections, so authentication is crucial.

189. Why should applications limit the number of form submission attempts?

A) To prevent brute-force attacks and automated form spam
B) To speed up form processing
C) To prevent users from submitting incorrect data
D) To allow only JSON-formatted input

✅ Answer: A) To prevent brute-force attacks and automated form spam
Explanation: Limiting form submissions reduces the risk of automated attacks.

191. Why should web applications restrict input fields to expected character sets?

A) To prevent encoding-based bypass attacks
B) To reduce server processing time
C) To improve form submission speed
D) To allow users to enter any input freely

✅ Answer: A) To prevent encoding-based bypass attacks
Explanation: Restricting input fields to expected character sets prevents attacks that use alternate encodings to bypass security controls.

192. What is the security risk of accepting unvalidated XML input in SOAP APIs?

A) It can lead to XML External Entity (XXE) attacks
B) It increases SOAP message size
C) It prevents SQL Injection
D) It makes API responses slower

✅ Answer: A) It can lead to XML External Entity (XXE) attacks
Explanation: SOAP APIs that accept unvalidated XML input may be vulnerable to XXE, allowing attackers to read server files or perform SSRF attacks.

193. How can an attacker exploit an improperly validated password reset token?

A) By predicting or manipulating the reset token
B) By sending multiple password reset requests
C) By using a complex password
D) By entering an incorrect username

✅ Answer: A) By predicting or manipulating the reset token
Explanation: Weak or predictable password reset tokens allow attackers to take over accounts.

194. Why should multi-step forms validate input at each step?

A) To prevent attackers from injecting malicious input at later steps
B) To make the form submission process slower
C) To allow users to submit partial forms
D) To ensure users type the correct input

✅ Answer: A) To prevent attackers from injecting malicious input at later steps
Explanation: Each step should be validated to prevent attackers from bypassing validation in earlier steps.

195. What is a major security risk of dynamically building database queries using user input?

A) SQL Injection
B) Cross-Site Scripting (XSS)
C) Denial of Service (DoS)
D) Buffer Overflow

✅ Answer: A) SQL Injection
Explanation: Allowing user input in dynamic SQL queries without parameterization makes SQL Injection possible.

196. What type of input validation should be applied to phone number fields?

A) Allow only numeric characters and enforce length restrictions
B) Accept all character types
C) Convert phone numbers to uppercase before storing
D) Store phone numbers as floating-point numbers

✅ Answer: A) Allow only numeric characters and enforce length restrictions
Explanation: Restricting phone numbers to numeric values prevents injection attacks and ensures valid formatting.

197. Why should web applications reject inputs that contain null characters (`%00`)?

A) Null characters can be used to bypass input validation mechanisms
B) They slow down form processing
C) They prevent session expiration
D) They increase database storage requirements

✅ Answer: A) Null characters can be used to bypass input validation mechanisms
Explanation: Attackers use null characters to bypass security filters and manipulate string termination in unsafe languages.

198. How does input validation help mitigate HTTP Parameter Pollution (HPP) attacks?

A) By enforcing strict rules on duplicate parameter handling
B) By allowing multiple parameters in a single request
C) By reducing network traffic
D) By converting all parameters to lowercase

✅ Answer: A) By enforcing strict rules on duplicate parameter handling
Explanation: HPP occurs when attackers manipulate duplicate parameters to override or bypass security controls.

199. What is a potential risk of allowing long and complex inputs in search fields?

A) Denial of Service (DoS) attacks through resource exhaustion
B) Slower query execution
C) Increased database storage
D) Improved search functionality

✅ Answer: A) Denial of Service (DoS) attacks through resource exhaustion
Explanation: Attackers can craft long or complex search queries to overload the database and cause DoS.

200. Why is input validation important for OAuth or Single Sign-On (SSO) implementations?

A) To prevent attackers from modifying authentication parameters
B) To speed up authentication requests
C) To improve session expiration handling
D) To encrypt authentication tokens

✅ Answer: A) To prevent attackers from modifying authentication parameters
Explanation: Attackers can manipulate OAuth parameters to gain unauthorized access if input validation is weak.

201. What is the security risk of accepting unrestricted input in a currency field?

A) Attackers can manipulate financial transactions
B) It slows down financial processing
C) It prevents SQL Injection
D) It prevents data corruption

✅ Answer: A) Attackers can manipulate financial transactions
Explanation: Unrestricted input can lead to financial fraud, such as negative transactions or currency conversion exploits.

202. How can developers prevent file extension spoofing attacks?

A) Validate both the file extension and MIME type
B) Allow users to rename files freely
C) Convert all files to .txt before storing
D) Store filenames in a database

✅ Answer: A) Validate both the file extension and MIME type
Explanation: Attackers may rename malicious files (e.g., .exe to .jpg), so both the extension and MIME type must be validated.

203. Why should application input validation rules be regularly updated?

A) To keep up with evolving attack techniques
B) To slow down form processing
C) To make error messages clearer
D) To improve application logging

✅ Answer: A) To keep up with evolving attack techniques
Explanation: New attack vectors emerge over time, requiring regular updates to input validation rules.

204. What is a risk of accepting input that is dynamically converted into system commands?

A) Command Injection attacks
B) XSS attacks
C) Slow execution time
D) Data corruption

✅ Answer: A) Command Injection attacks
Explanation: Allowing user input in system commands without proper validation enables attackers to execute arbitrary commands.

205. Why should web applications validate the `Content-Type` header in HTTP requests?

A) To prevent attacks that manipulate the request body format
B) To speed up HTTP request processing
C) To improve compatibility with mobile devices
D) To increase response times

✅ Answer: A) To prevent attacks that manipulate the request body format
Explanation: Attackers can modify Content-Type headers to bypass security filters and exploit weaknesses in request handling.

206. What is a major risk of allowing unvalidated input in a file upload feature?

A) Remote Code Execution (RCE) via malicious file uploads
B) Increased server storage usage
C) Slower file upload speeds
D) Corrupted file names

✅ Answer: A) Remote Code Execution (RCE) via malicious file uploads
Explanation: Attackers can upload and execute malicious files if validation is not enforced.

207. What is a security risk of allowing unrestricted wildcard characters in search queries?

A) Information disclosure through enumeration
B) Improved search accuracy
C) Faster query execution
D) Prevents brute-force attacks

✅ Answer: A) Information disclosure through enumeration
Explanation: Wildcard searches can allow attackers to enumerate sensitive data if restrictions are not applied.

208. How does client-side input validation impact security?

A) It improves user experience but does not replace server-side validation
B) It makes server-side validation unnecessary
C) It prevents all types of injection attacks
D) It slows down form submissions

✅ Answer: A) It improves user experience but does not replace server-side validation
Explanation: Client-side validation enhances usability but can be bypassed, making server-side validation critical.

211. Why should applications reject HTTP requests with an empty `User-Agent` header?

A) It may indicate bot or automated scanner activity
B) It increases network latency
C) It prevents SQL injection
D) It improves page rendering

✅ Answer: A) It may indicate bot or automated scanner activity
Explanation: Attackers often strip or modify the User-Agent header to bypass security mechanisms or perform reconnaissance.

212. What is the primary risk of allowing users to modify hidden form fields?

A) It enables unauthorized actions like privilege escalation
B) It makes form submission slower
C) It improves user experience
D) It reduces browser compatibility issues

✅ Answer: A) It enables unauthorized actions like privilege escalation
Explanation: Attackers can tamper with hidden form fields to escalate privileges, modify transaction values, or bypass security checks.

213. How can developers prevent attackers from bypassing input validation by using encoded characters?

A) Normalize and decode input before validation
B) Accept only uppercase letters in input fields
C) Store input in encrypted form
D) Convert all input into JSON format

✅ Answer: A) Normalize and decode input before validation
Explanation: Attackers can use URL encoding, Unicode encoding, or other encoding techniques to bypass validation. Normalizing input ensures security filters work correctly.

214. What is a common issue when allowing unrestricted HTML input in a content management system (CMS)?

A) It can lead to Stored Cross-Site Scripting (XSS) attacks
B) It increases the load time of web pages
C) It prevents database indexing
D) It makes text formatting harder

✅ Answer: A) It can lead to Stored Cross-Site Scripting (XSS) attacks
Explanation: Malicious users can insert JavaScript into HTML content, which is then executed when other users view the page.

215. How does input validation help prevent privilege escalation attacks?

A) By ensuring users cannot modify access control parameters
B) By encrypting all user data before processing
C) By storing user input in session variables
D) By converting all user input to lowercase

✅ Answer: A) By ensuring users cannot modify access control parameters
Explanation: Attackers may try to modify roles, permissions, or other security parameters via input tampering. Proper validation prevents this.

216. Why should applications reject excessively deep JSON objects in API requests?

A) To prevent JSON-based Denial-of-Service (DoS) attacks
B) To improve API response speed
C) To allow unlimited nesting for flexibility
D) To improve JSON parsing speed

✅ Answer: A) To prevent JSON-based Denial-of-Service (DoS) attacks
Explanation: Deeply nested JSON objects can cause excessive memory usage and processing delays, leading to DoS attacks.

217. What is a primary risk of allowing unrestricted URL redirections in an application?

A) Open Redirect attacks, leading to phishing and malware distribution
B) Slower page load times
C) Reduced SEO rankings
D) Increased server resource consumption

✅ Answer: A) Open Redirect attacks, leading to phishing and malware distribution
Explanation: Attackers can manipulate URL parameters to redirect users to malicious sites, often used for phishing.

218. Why should web applications validate uploaded image files?

A) To prevent steganography-based malware embedding
B) To improve image rendering speed
C) To allow larger file uploads
D) To reduce database storage usage

✅ Answer: A) To prevent steganography-based malware embedding
Explanation: Malicious payloads can be hidden inside image files and later extracted for execution.

219. What is a security risk of allowing unrestricted HTML attributes in user input?

A) Attackers can insert event-based JavaScript (e.g., onerror, onmouseover) for XSS attacks
B) It slows down page rendering
C) It prevents SQL Injection
D) It improves user customization

✅ Answer: A) Attackers can insert event-based JavaScript (e.g., onerror, onmouseover) for XSS attacks
Explanation: Certain HTML attributes trigger JavaScript execution when an event occurs, enabling XSS attacks.

Input Validation & Sanitization – Stopping Injection Attacks