Question 630
A password-change API accepts simultaneous requests but applies different validation rules depending on timing. Which evidence most strongly validates the intended interpretation or control?
Explanation
Correct Answer
A controlled concurrency test cannot produce an unauthorized state transition. This answer directly addresses the described constraint. Race conditions can bypass checks when state is updated nonatomically. Successful validation requires: A controlled concurrency test cannot produce an unauthorized state transition.
Incorrect Answers
It would address a web gateway trusts an unsigned JWT claim that a user is an administrator. The relevant reason in that case is: Untrusted token content must never grant privileged API access. Here the required success condition is a controlled concurrency test cannot produce an unauthorized state transition. The relevant evidence is: A controlled concurrency test cannot produce an unauthorized state transition.
This result applies to a different case: A JSON Web Token API accepts tokens with an unexpected algorithm or mismatched audience. JWT validation requires more than decoding a base64 payload. It does not establish the present requirement, where a controlled concurrency test cannot produce an unauthorized state transition. The relevant evidence is: A controlled concurrency test cannot produce an unauthorized state transition.
That approach concerns a different situation: an OAuth API lets a read-only token change a different user's account settings. A valid token is insufficient when it lacks the required action or object access. The required result is that a controlled concurrency test cannot produce an unauthorized state transition. The relevant evidence is: A controlled concurrency test cannot produce an unauthorized state transition.