Masteriyo LMS < 3.4.2 - Subscriber+ Arbitrary User Course Progress Disclosure via IDOR

The Masteriyo LMS WordPress plugin before 3.4.2 does not verify that the user making the request owns the course-progress records being returned, allowing any authenticated user, such as a self-registered subscriber, to read another user's learning activity. The ownership check it applies is skipped whenever the requested account is not named with a non-zero value, in which case the records of every learner on the site are returned at once.