Application Security Checklist

Input Validation and Output Encoding

[Critical] Implement input validation for all user inputs
[High] Use parameterized queries to prevent SQL injection
[High] Implement proper output encoding to prevent XSS attacks
[Medium] Validate and sanitize all file uploads
[Medium] Implement proper character encoding

Authentication and Session Management

[Critical] Implement strong password policies
[High] Use multi-factor authentication (MFA)
[High] Implement secure session management
[Medium] Use secure password storage (e.g., bcrypt, Argon2)
[Medium] Implement account lockout mechanisms

Access Control

[Critical] Implement the principle of least privilege
[High] Use role-based access control (RBAC)
[High] Implement proper authorization checks
[Medium] Validate user permissions on the server-side
[Medium] Implement proper access controls for API endpoints

Cryptography

[Critical] Use strong, up-to-date encryption algorithms
[High] Implement proper key management
[High] Use TLS for all connections
[Medium] Implement proper certificate validation
[Medium] Use secure random number generation

Error Handling and Logging

[High] Implement proper error handling
[High] Avoid exposing sensitive information in error messages
[Medium] Implement secure logging practices
[Medium] Monitor and alert on suspicious activities
[Low] Implement proper log rotation and retention policies

Data Protection

[Critical] Encrypt sensitive data at rest
[High] Implement proper data classification
[High] Use secure protocols for data transmission
[Medium] Implement data masking for sensitive information
[Medium] Implement proper data retention and deletion policies

Third-Party Components

[High] Regularly update third-party libraries and frameworks
[High] Use dependency scanning tools
[Medium] Maintain an inventory of third-party components
[Medium] Verify the integrity of third-party components
[Low] Review licenses of third-party components

Security Testing

[High] Conduct regular security assessments
[High] Perform penetration testing
[Medium] Use automated security scanning tools
[Medium] Implement security unit tests
[Low] Conduct code reviews with a security focus

Secure Development Lifecycle

[High] Implement secure coding standards
[High] Provide security training for developers
[Medium] Implement a vulnerability management process
[Medium] Use threat modeling in the design phase
[Low] Maintain security documentation

Note: This checklist provides a general overview of application security best practices. The specific measures you need to implement may vary depending on your application's architecture, technology stack, and specific requirements. Always consult with security professionals and stay informed about the latest security trends and threats in application development.