Which practice defends against file injection?

Which practice defends against file injection?

• A. Strongly validate user input.
• B. Define access rights.
• C. Keep OS up to date.
• D. Implement cookie's timeout.

Answer: (A)

Strongly validating user input is the best defense against file injection because many injection flaws arise when an application uses untrusted input to build file names, paths, or contents. By validating and sanitizing input on the server side, you prevent attackers from supplying characters or patterns that would alter which file is opened, read, or written (such as path traversal attempts or crafted file names). Techniques include using strict allowlists, canonicalizing paths, enforcing length limits, and avoiding direct use of raw user data in file operations. This reduces the chance that malicious input can manipulate file handling. Defining access rights helps limit what a file or process can do once accessed, but it doesn’t stop the initial manipulation of file-related input. Keeping the operating system up to date reduces overall vulnerabilities but doesn’t specifically address improper handling of user-supplied file data. Implementing a cookie timeout relates to session management and does not impact how files are validated or processed.

Strongly validating user input is the best defense against file injection because many injection flaws arise when an application uses untrusted input to build file names, paths, or contents. By validating and sanitizing input on the server side, you prevent attackers from supplying characters or patterns that would alter which file is opened, read, or written (such as path traversal attempts or crafted file names). Techniques include using strict allowlists, canonicalizing paths, enforcing length limits, and avoiding direct use of raw user data in file operations. This reduces the chance that malicious input can manipulate file handling.

Defining access rights helps limit what a file or process can do once accessed, but it doesn’t stop the initial manipulation of file-related input. Keeping the operating system up to date reduces overall vulnerabilities but doesn’t specifically address improper handling of user-supplied file data. Implementing a cookie timeout relates to session management and does not impact how files are validated or processed.