The Masteriyo LMS WordPress plugin before 3.4.0 does not perform any authorization check before returning a course enrolment record over its REST API, allowing unauthenticated users to read any learner's enrolment status, timestamps and course-progress data by walking sequential record identifiers. A related gap lets any enrolled user retrieve other learners' enrolment records as well.
https://wpscan.com/vulnerability/a6e580be-ce42-479d-97cd-fcfa2f752b2c/