The Masteriyo LMS WordPress plugin before 3.4.0 does not sanitise and escape some course settings before outputting them in a page available to all visitors, allowing users with a course-author role to perform Stored Cross-Site Scripting attacks that run in the session of anyone viewing the course, including a logged-in administrator.

The Masteriyo LMS WordPress plugin before 2.3.3 does not sanitise and escape a quiz field before outputting it back in a page, and grants its instructor role the ability to store unfiltered HTML, allowing such users to perform Stored Cross-Site Scripting attacks against any visitor of the affected page, including administrators. This affects default single-site installations. Sites running multisite, or defining DISALLOWUNFILTEREDHTML, are not affected as the capability is not granted there.

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.