API changes deserve careful review because they reshape the way other systems talk to your application. A small change can create a large security impact if it weakens auth, widens access, or leaks data in a response payload.
Review the contract
Every API change should make its contract obvious: what inputs it accepts, what it returns, who can call it, and what errors it might expose. If that contract is unclear in the code, the review should slow down.
Check the security surfaces
- Authentication and authorization
- Input validation
- Output filtering and redaction
- Rate limiting and abuse handling
- Error messages and logging
Common API mistakes
- Endpoints that trust client-provided IDs too much
- Response fields that reveal internal state
- Missing checks on update and delete operations
- Version changes that break old clients in unsafe ways
What a good reviewer confirms
A secure API review confirms that the new endpoint or modification behaves as intended, protects data boundaries, and fails safely when something goes wrong.