# CVE-2026-18439: Tutor LMS insecure direct object reference in quiz builder

Source: https://junglewise.ai/threats/cve-2026-18439-the-tutor-lms-elearning-and-online-course-solution-plugin-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-18439 · Severity: medium · CVSS 4.3 · Published 2026-09-22

Tutor LMS is a WordPress plugin that powers online course platforms and learning management systems. An authenticated attacker with instructor-level privileges can modify, delete, or reassign quiz questions and answers belonging to other instructors or administrators by bypassing authorization checks, leading to course content tampering and data loss.

Technologies: [Themeum Tutor LMS](https://junglewise.ai/threats/technologies/tutor-lms). Vendors: [Themeum](https://junglewise.ai/threats/vendors/themeum).

## Quick answers

**Is CVE-2026-18439 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-18439 being exploited in the wild.

**How severe is CVE-2026-18439?** Medium severity, with a CVSS score of 4.3, published 22 September 2026.

**Which products and versions are affected?** Themeum Tutor LMS up to and including 4.0.7.

**Is there a fix for CVE-2026-18439?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-18439 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-18439?** Check whether you run Themeum Tutor LMS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an insecure direct object reference (IDOR) in the tutor_quiz_builder_save AJAX action, where the handler validates top-level course_id and topic_id but passes nested question_id, answer_id, deleted_question_ids[], and deleted_answer_ids[] directly into database update and delete operations without verifying ownership. An authenticated attacker with Instructor-level access can craft requests to overwrite quiz questions and answers belonging to other instructors, or delete arbitrary question and answer records via QuizBuilder::save_questions(), QuizBuilder::save_question_answers(), and QuizBuilder::handle_delete() functions.

## Affected products

- Themeum Tutor LMS up to and including 4.0.7

## Timeline

- 2026-09-22: disclosed

## References

- [https://plugins.trac.wordpress.org/browser/tutor/tags/3.9.10/classes/QuizBuilder.php](https://plugins.trac.wordpress.org/browser/tutor/tags/3.9.10/classes/QuizBuilder.php)
- [https://plugins.trac.wordpress.org/browser/tutor/tags/3.9.10/classes/QuizBuilder.php](https://plugins.trac.wordpress.org/browser/tutor/tags/3.9.10/classes/QuizBuilder.php)

## Related threats

- [Tutor LMS insecure direct object reference in API routing](https://junglewise.ai/threats/cve-2026-93779-the-tutor-lms-elearning-and-online-course-solution-plugin-for)
- [Themeum Tutor LMS stored cross-site scripting](https://junglewise.ai/threats/cve-2026-111407-improper-neutralization-of-input-during-web-page-generation)
- [Tutor LMS insecure direct object reference in course update](https://junglewise.ai/threats/cve-2026-92715-the-tutor-lms-elearning-and-online-course-solution-plugin-for)
- [Tutor LMS stored cross-site scripting via display_name](https://junglewise.ai/threats/cve-2026-93681-the-tutor-lms-elearning-and-online-course-solution-plugin-for)
- [Themeum Tutor LMS reflected cross-site scripting vulnerability](https://junglewise.ai/threats/cve-2026-42702-improper-neutralization-of-input-during-web-page-generation-cross)