FAQ-001012 - File Upload Security / Unrestricted File Upload Prevention

"Unrestricted File Upload" occurs when users can upload files without proper validation or restrictions, which can lead to security risks like unauthorized access, data breaches, or malicious file execution. **Required Security Measures and Restrictions:** **Basic Restrictions:** 1. **Validate File Types and Sizes**: Allow only permitted formats and sizes. Restrict uploads to necessary file types by validating file extensions and MIME types. 2. **Set File Size Limits**: Define and enforce a maximum file size for uploads. 3. **Sanitize File Names**: Remove or escape special characters in file names to prevent injection attacks. **Secure Implementation:** 4. **Secure Upload Methods**: Use components like `lightning-file-upload` for secure file uploads. 5. **Associate Files with Records**: Use triggers on the `ContentVersion` object to create `ContentDocumentLink` records. 6. **Store Files Securely**: Use secure storage mechanisms and avoid publicly accessible locations without proper access controls. 7. **Use Secure Communication**: Ensure uploads occur over secure channels like HTTPS. **Advanced Security Measures:** 8. **Scan for Malware**: Integrate antivirus or malware scanning tools to check uploaded files. 9. **Access Control**: Enforce CRUD/FLS checks and sharing rules for file-related operations. Use `WITH USER_MODE` for SOQL queries and `AccessLevel.USER_MODE` for Database methods to automatically enforce permissions. Ensure only authorized users can upload or access files. 10. **Avoid Executable Content**: Prevent the upload of executable files or scripts. 11. **Implement Content Security Policies (CSP)**: Prevent execution of malicious scripts or files. 12. **Log and Monitor**: Keep logs of upload activities and monitor for unusual behavior. **Additional Measures:** 13. **Protect Sensitive Data**: Avoid exposing sensitive tokens or data during file uploads. 14. **Secure Storage**: Use encryption and secure mechanisms for sensitive files. 15. **File Cleanup**: Regularly review and remove standalone files not associated with records. 16. **Document Your Approach**: Clearly document your file upload handling approach in your submission. 17. **Thorough Testing**: Test your implementation thoroughly before submitting for review. By following these practices, you can mitigate risks, align with AppExchange security standards, and ensure a secure and controlled file upload process.

The FAQ content is comprehensive and accurate, with only one minor improvement needed. In point 9 about access control, I updated the wording to prioritize modern security enforcement approaches by mentioning `WITH USER_MODE` and `AccessLevel.USER_MODE` first, following the security approaches guidelines to lead with modern features while maintaining the existing content structure. Regarding security rules selection: **ApexCRUDViolation**: Directly relates to point 9's emphasis on "Enforce CRUD/FLS checks for file-related operations" - this rule detects violations of CRUD permissions in Apex code that handles file operations. **ApexSharingViolations**: Connects to point 9's requirement to "enforce sharing rules for file-related operations" - this rule identifies when sharing violations occur in Apex code managing file access. **ProtectSensitiveData**: Relates to point 13's guidance to "Avoid exposing sensitive tokens or data during file uploads" - this rule helps detect when sensitive data might be exposed inappropriately. **ApexInsecureEndpoint**: Connects to point 7's requirement for "secure communication over HTTPS" and general secure upload implementation - this rule identifies insecure endpoint configurations. **ApexXSSFromEscapeFalse**: Relates to point 3's "Sanitize File Names" and point 11's "Implement Content Security Policies" - this rule detects XSS vulnerabilities from unescaped content, which is relevant when handling file names and preventing script execution. **ApexXSSFromURLParam**: Connects to the overall file upload security context where user input (including file parameters) needs proper validation and escaping to prevent XSS attacks, supporting points 1 and 3 about validation and sanitization.