CVE-2025-6639 Overview
CVE-2025-6639 affects the Tutor LMS Pro WordPress plugin, an eLearning and online course solution used by course creators. The vulnerability is an Insecure Direct Object Reference (IDOR) [CWE-285] in the tutor_assignment_submit() function. All versions up to and including 3.8.3 fail to validate a user-controlled key when viewing and editing assignments. Authenticated users with Subscriber-level access or higher can view and modify assignment submissions belonging to other students. The flaw enables horizontal privilege escalation across student accounts on affected learning platforms.
Critical Impact
Authenticated attackers with Subscriber-level access can read and tamper with any student's assignment submission, compromising course integrity and student data confidentiality.
Affected Products
- Tutor LMS Pro plugin for WordPress, all versions up to and including 3.8.3
- WordPress sites using the affected plugin for course delivery
- Learning platforms accepting Subscriber-level registrations
Discovery Timeline
- 2025-10-25 - CVE-2025-6639 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-6639
Vulnerability Analysis
The vulnerability resides in the tutor_assignment_submit() function, which handles viewing and editing of student assignment submissions. The function accepts a user-controlled key that identifies the target submission but does not verify that the requesting user owns that submission. An attacker authenticated at Subscriber level can supply an arbitrary submission identifier and receive or modify data belonging to another enrolled student.
The issue falls under Insecure Direct Object Reference, a broken access control pattern classified under Improper Authorization [CWE-285]. Impact is limited to confidentiality and integrity of assignment content; availability is not affected. Because the plugin is aimed at commercial course delivery, exploitation can compromise grading integrity and expose personal work product.
Root Cause
The root cause is missing authorization validation between the authenticated session and the requested submission object. The tutor_assignment_submit() handler trusts the supplied key without confirming that the current user is the owner of the referenced submission or holds an instructor role for the associated course.
Attack Vector
Exploitation requires network access to the WordPress site and a valid account at Subscriber level or higher. Many Tutor LMS deployments allow self-service registration, which lowers the barrier significantly. The attacker sends a crafted request to the assignment submission endpoint, substituting the submission identifier of a targeted student. The server returns or updates the submission without an ownership check.
See the Wordfence Vulnerability Report for additional technical detail on the affected function.
Detection Methods for CVE-2025-6639
Indicators of Compromise
- Unexpected edits to assignment submissions attributed to accounts other than the enrolled student
- Subscriber-level accounts issuing repeated requests to the tutor_assignment_submit AJAX action with varying submission keys
- Access logs showing sequential or enumerated submission identifiers from a single session
Detection Strategies
- Review web server access logs for high-frequency POST requests to admin-ajax.php with action=tutor_assignment_submit from low-privilege accounts
- Correlate submission modification events in the WordPress database with the authenticated user ID to identify ownership mismatches
- Enable WordPress audit logging to capture assignment view and edit events with source user context
Monitoring Recommendations
- Monitor for spikes in Subscriber-level authentication followed by rapid assignment endpoint access
- Alert on any assignment submission update where the acting user differs from the submission owner
- Track newly registered Subscriber accounts that immediately interact with LMS AJAX endpoints
How to Mitigate CVE-2025-6639
Immediate Actions Required
- Update Tutor LMS Pro to a version later than 3.8.3 as soon as the vendor publishes a patched release
- Audit recent assignment submissions for unauthorized modifications by comparing author metadata against expected enrollment records
- Disable open self-registration on affected WordPress sites until patching is complete
Patch Information
At the time of publication, refer to the Tutor plugin page on WordPress.org for the latest release information. Site administrators should apply the vendor-supplied fix that adds ownership validation to the tutor_assignment_submit() handler. Consult the Wordfence advisory for the fixed version number once published.
Workarounds
- Restrict Subscriber-level registration to trusted users until the plugin is updated
- Deploy a web application firewall rule blocking tutor_assignment_submit requests where the submission key does not match the session user
- Temporarily disable assignment submission features via the plugin settings if immediate patching is not possible
- Increase database backup frequency to enable rollback of tampered submissions
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.