Tutor LMS <= 4.0.0 - Authenticated (Subscriber+) SQL Injection via Stored Quiz Answer Array

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to generic SQL Injection via Stored Quiz Answer Array in all versions up to, and including, 4.0.0 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with custom-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. The payload is stored at quiz-attempt time via the wp_ajax_tutor_quiz_abandon handler, but the injected SQL executes only when a privileged user or Tutor REST API key holder requests the /wp-json/tutor/v1/quiz-attempt-details/{id} endpoint, making this a second-order (stored) injection chain.