Quiz and Survey Master (QSM) < 11.1.5 - Missing Authorization to Authenticated (Contributor+) Arbitrary Quiz Modification and Email Reroute via Leaked Nonce from /quiz/structure

Description

The Quiz and Survey Master (QSM) – Easy Quiz and Survey Maker plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 11.1.4. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with contributor-level access and above, to modify quizzes they do not own, overwrite quiz results pages, and reroute quiz-result notification emails to attacker-controlled addresses. An attacker first calls the /quiz/structure endpoint with an arbitrary victim quiz ID to obtain a valid nonce bound to that quiz ID and their own user ID, then presents that nonce to the /quizzes/{id}/emails save endpoint, which accepts it without verifying quiz ownership.