What are the most critical API security flaws being overlooked by modern dev teams?

All answers to this question.

In my experience, the absolute biggest mistake is relying entirely on client-side validation and neglecting broken object level authorization (BOLA). Developers frequently expose internal object IDs in the API URL string, assuming that because a user is authenticated, they have the right to access any resource. This allows attackers to simply manipulate the ID numbers in the request to access other users' private data. You must implement robust, server-side authorization checks for every single API call, validating that the logged-in session actually owns the requested resource ID before returning any data.

   Answered 2025-03-18 by Megan Foster

Aren't these authorization issues easily caught by standard automated vulnerability scanners during the CI/CD pipeline, or do they require manual penetration testing?

   Answered 2025-03-19 by Brian O'Connor

• Automated scanners usually miss BOLA because they don't understand business logic. A scanner sees a valid 200 OK response and assumes everything is fine, completely unaware that User A just successfully requested User B's private account details. You really need custom security tests or manual code reviews to catch these flaws before production.

     Commented 2025-03-21 by Kevin Blake

Another massive oversight is mass assignment. This occurs when frameworks automatically bind user input directly to software models, allowing attackers to update sensitive backend database fields they shouldn't touch.

   Answered 2025-03-22 by Charles Vance

• Spot on, Charles. I always recommend using Data Transfer Objects (DTOs) or strict whitelisting to explicitly define which fields are allowed to be updated by the API client, blocking payload injections completely.

     Commented 2025-03-23 by Rachel Green