Tutor LMS <= 3.9.9 - Insecure Direct Object Reference to Authenticated (Instructor+) Arbitrary Post Deletion via 'course' GET Parameter

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to and including 3.9.9. This is due to the `get_course_id_by()` function unconditionally trusting the user-supplied `course` GET parameter as the authoritative course ID for content ownership lookups, which is then consumed by `can_user_manage()`, the plugin's sole authorization gate for instructor-level operations, causing it to evaluate instructor membership against the attacker-controlled course rather than the course that actually owns the target content object. This makes it possible for authenticated attackers, with instructor-level access and above, to perform unauthorized operations on any other instructor's course content, including permanently deleting lessons, assignments, quizzes (with cascading deletion of all student attempt data), topics, announcements, and Q&A threads, as well as creating or modifying lessons, topics, and announcements in victim courses, manipulating student quiz grades, and reading unpublished lesson and quiz content.