CVE-2025-67857 Overview
A flaw was found in Moodle where user identifiers are inadvertently exposed in URLs during anonymous assignment submissions. This information disclosure vulnerability allows unauthorized viewers to see internal user IDs, compromising the intended anonymity of assignment submissions and potentially leading to broader information disclosure issues.
Critical Impact
User anonymity is compromised during anonymous assignment submissions, exposing internal user IDs through URL parameters and defeating the privacy protections intended by the anonymous submission feature.
Affected Products
- Moodle Learning Management System (affected versions not specified in advisory)
Discovery Timeline
- 2026-02-03 - CVE-2025-67857 published to NVD
- 2026-02-03 - Last updated in NVD database
Technical Details for CVE-2025-67857
Vulnerability Analysis
This vulnerability is classified under CWE-201 (Insertion of Sensitive Information Into Sent Data), which occurs when sensitive information is included in data sent to an external component without proper sanitization or protection. In the context of Moodle's anonymous assignment feature, the application fails to properly obscure user identifiers when constructing URLs, inadvertently leaking these identifiers to unauthorized parties.
The anonymous assignment feature in Moodle is designed to allow students to submit work without revealing their identity to graders, promoting unbiased evaluation. However, this implementation flaw undermines that privacy guarantee by embedding user IDs directly into URL parameters that are visible to anyone with access to the page source, browser history, or network traffic.
Root Cause
The root cause of this vulnerability lies in improper handling of user identifiers within the URL generation logic for anonymous assignment submissions. When Moodle constructs URLs for anonymous submission workflows, it includes internal user IDs as URL parameters rather than using anonymized tokens or session-based identifiers. This design oversight exposes sensitive user identification data in a context where anonymity is explicitly expected and required.
Attack Vector
The vulnerability is exploitable via network access and requires user interaction. An attacker could exploit this flaw through several scenarios:
Direct URL Observation: Anyone with access to the submission page (such as a teaching assistant or co-instructor) can observe user IDs in the browser address bar or by inspecting page source code.
Network Traffic Analysis: User IDs could be captured through proxy logs, browser history, or network monitoring tools, especially in shared computing environments.
Referrer Leakage: If the submission page links to external resources, the user ID may be leaked via the HTTP Referer header.
The attack requires minimal technical sophistication—simply observing URL parameters reveals the user identifiers that should remain hidden during anonymous submissions.
Detection Methods for CVE-2025-67857
Indicators of Compromise
- Unexpected user ID parameters visible in Moodle assignment submission URLs (e.g., ?userid= or similar parameters in anonymous assignment contexts)
- Unusual access patterns to anonymous assignment pages combined with subsequent targeted actions toward specific users
- Evidence of URL harvesting or parameter enumeration in web server access logs
Detection Strategies
- Monitor web server logs for requests to anonymous assignment endpoints that contain user identifier parameters
- Implement URL pattern analysis to detect user ID exposure in anonymous submission contexts
- Review browser network traffic for parameter leakage in assignment-related requests
- Audit referrer headers in outbound requests from Moodle assignment pages
Monitoring Recommendations
- Enable detailed logging for the Moodle assignment module, particularly for anonymous submission features
- Monitor for unusual patterns of user ID lookups following anonymous assignment access
- Implement alerting for requests that combine anonymous assignment endpoints with explicit user identification parameters
- Regularly review Moodle security advisories and forum discussions for related issues
How to Mitigate CVE-2025-67857
Immediate Actions Required
- Review and apply the latest Moodle security updates as they become available
- Audit current anonymous assignment submissions for potential privacy breaches
- Consider temporarily disabling anonymous assignment features if user privacy is critical until patches are applied
- Review web server logs to identify if any exploitation has occurred
Patch Information
Administrators should consult the official Moodle security resources for patch availability. For detailed information about this vulnerability and remediation guidance, refer to the following resources:
Workarounds
- Disable anonymous assignment submissions until the vulnerability is patched if strict user anonymity is required
- Use alternative anonymization methods such as manually-assigned anonymous identifiers managed outside of Moodle
- Implement web application firewall rules to strip or obscure user ID parameters from anonymous assignment URLs
- Educate staff with grading access about the potential for inadvertent user identification and request discretion
No verified code examples are available for this vulnerability. Administrators should refer to the official Moodle security advisories and Red Hat resources linked above for technical implementation details regarding the fix.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
