CVE-2026-18439: themeum tutor lms – elearning and online course solution

Vulnerability summary

CVE-2026-18439 is a medium (CVSS 4.3) vulnerability in themeum tutor lms – elearning and online course solution. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.4% of scored vulnerabilities. Fixed in 4.0.8.

Timeline

1. 22-09-2026
   PublishedVulnerability first disclosed.
2. 23-09-2026
   Last modifiedVulnerability information updated.

Description

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 4.0.7 via the tutor_quiz_builder_save AJAX action due to missing validation that nested question_id, answer_id, deleted_question_ids[], and deleted_answer_ids[] values in the submitted payload belong to a quiz/topic/course the requester is authorized to manage. The handler only validates the top-level course_id, topic_id, and (when supplied) payload['ID'], but the nested identifiers are passed straight into $wpdb->update/DELETE statements in QuizBuilder::save_questions(), QuizBuilder::save_question_answers(), and QuizBuilder::handle_delete(). This makes it possible for authenticated attackers, with Instructor-level access and above, to overwrite the content and re-parent arbitrary quiz questions/answers belonging to other instructors or administrators, and to delete arbitrary quiz question and answer rows.

• CWE-639Authorization Bypass Through User-Controlled KeyThe system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.