A REST API uses user-provided object IDs without authorization checks.

The correct answer is D, BOLA, or Broken Object Level Authorization. This occurs when an API accepts an object identifier supplied by the user, such as an account ID, order ID, invoice ID, or user ID, but fails to verify whether the authenticated user is authorized to access that specific object. CEH web application hacking material describes this same weakness as an authorization flaw/insecure direct object reference: an application uses IDs to distinguish users, and an attacker changes an ID value in the request to access another user’s profile. CEH material also explains that unauthorized access to another user’s resources represents horizontal privilege escalation and that function-level access issues occur when the application does not check authorization before returning protected information. Mass assignment involves binding unexpected fields, XSS involves script injection, and SQLi involves malicious database queries. The key issue here is missing object-level authorization, so BOLA is the best answer.