Academy LMS < 3.8.3 - Subscriber+ Arbitrary Lesson Content Disclosure via lessons REST Endpoint

The Academy LMS WordPress plugin before 3.8.3 does not verify course enrollment or lesson publication status when returning a single lesson through its REST API, allowing users with a self-service student (Subscriber-level) account to disclose the content of arbitrary lessons, including lessons of paid courses they are not enrolled in and unpublished (draft, pending, private) lessons.