CVE-2026-18439

Tutor LMS <= 4.0.7 - Authenticated (Custom+) Insecure Direct Object Reference to Arbitrary Quiz Question/Answer Modification and Deletion via 'payload' Parameter

2026-09-21 18:52
Nakul Chodha

Strategic Overview

Status
Patched in 4.0.8
Affected Version
<= 4.0.7
CVSS
4.3Medium
Weakness type
CWE-639 · Authorization Bypass Through User-Controlled Key
CVE
CVE-2026-18439
View all Tutor LMS – eLearning and online course solution vulnerabilities

At a glance

CVE-2026-18439 is a medium-severity Authorization Bypass Through User-Controlled Key vulnerability in the Tutor LMS WordPress plugin, affecting versions <= 4.0.7. It carries a CVSS score of 4.3 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Custom level or above. The issue is fixed in version 4.0.8; sites on affected versions should update now. Disclosed September 2026, reported by Nakul Chodha.

Vulnerability Overview

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.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user.

CWE-639: Authorization Bypass Through User-Controlled Key

Tutor LMS <= 4.0.7 carries this weakness at save_questions(), and reaching it takes an account at Custom level or above. Authorization bypass through a user-controlled key, often called insecure direct object reference, means the application looks up a record by an identifier from the request without checking that the caller owns it.

Changing a number in the request is enough to read or modify other users' records, which on commerce and membership sites means customer data. For Tutor LMS the fix is 4.0.8: builds <= 4.0.7 are affected, anything from 4.0.8 onward is not.

Remediation

Update to version 4.0.8, or a newer patched version

How does WordSec protect against this?

Because it turns on account access, WordSec's login security is the relevant layer: role-based two-factor, captcha and brute-force limits raise the cost of getting the account this needs. None of that substitutes for the fix: Tutor LMS 4.0.8 closes this, and updating the plugin is the step that ends it.

  • Login Security
  • Alerts

External References

Related records

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