Your API works. Do its access controls?
Why testing customer and permission boundaries deserves a place in your security review.
A valid login is only the beginning
Authentication establishes who a user is. Authorization decides what that user may do. An API can authenticate every request and still expose a record or action to the wrong person. A security review should examine both controls in the context of the application’s roles and data boundaries.
Map the important boundaries
Document which roles may access which objects and actions. Include customers, support users, administrators and machine accounts where relevant. For a multi-tenant product, identify how the application enforces organization separation. This map becomes a practical reference for test cases and remediation discussions.
Test the expected behavior
Use authorized test accounts and synthetic records to review permitted and denied access. Include different roles and organizations in the agreed scope. Check sensitive operations as well as read access. Keep the review within the written rules of engagement and avoid real customer data wherever possible.
Fix the boundary, then verify it
The useful result is a clear description of the missing control, the affected workflow and a reproducible test. After remediation, verify the original finding and related paths. Building regression checks around these boundaries helps keep the same class of weakness from returning as the API evolves.