CVE-2025-67855
📋 TL;DR
A reflected Cross-Site Scripting (XSS) vulnerability in Moodle's policy tool return URL allows attackers to inject malicious scripts through specially crafted links. This could lead to information disclosure or arbitrary script execution in users' browsers. All Moodle instances with vulnerable versions are affected.
💻 Affected Systems
- Moodle
📦 What is this software?
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, credentials, or sensitive user data, potentially leading to account takeover or data breaches.
Likely Case
Attackers could perform session hijacking, redirect users to malicious sites, or deface parts of the application.
If Mitigated
With proper input validation and output encoding, the risk is minimal as malicious scripts would be neutralized.
🎯 Exploit Status
Exploitation requires tricking users into clicking malicious links; no authentication needed for the attack vector.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Moodle security advisories for specific patched versions
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2025-67855
Restart Required: No
Instructions:
1. Check Moodle's official security advisory for the patched version. 2. Update Moodle to the latest secure version. 3. Verify the fix by testing the policy tool functionality.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement server-side validation and sanitization of URL parameters in the policy tool.
Content Security Policy (CSP)
allDeploy a strict CSP header to mitigate XSS impact by restricting script execution sources.
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block malicious URL parameters.
- Educate users to avoid clicking untrusted links and monitor for suspicious activity.
🔍 How to Verify
Check if Vulnerable:
Test by injecting a simple script payload into the policy tool return URL parameter and check if it executes.Check Version:
Check Moodle version via admin panel or configuration files.Verify Fix Applied:
After patching, repeat the test to ensure script injection is blocked or sanitized.📡 Detection & Monitoring
Log Indicators:
- Unusual URL parameters in policy tool requests, especially with script tags or JavaScript code.
Network Indicators:
- HTTP requests with malicious payloads in URL parameters to the policy tool endpoint.
SIEM Query:
Search for URLs containing 'policy' and suspicious patterns like '<script>' or 'javascript:' in query strings.