CVE-2025-66939
📋 TL;DR
This Cross-Site Scripting vulnerability in 66biolinks allows attackers to inject malicious scripts via crafted favicon files, potentially compromising user sessions and data. It affects all users of 66biolinks version 61.0.1 who process untrusted favicon uploads.
💻 Affected Systems
- 66biolinks by AltumCode
📦 What is this software?
66biolinks by Altumcode
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover, session hijacking, credential theft, and malware distribution to all users accessing the compromised page.
Likely Case
Session hijacking of users who interact with malicious favicon uploads, potentially leading to unauthorized access to user accounts.
If Mitigated
Limited impact with proper input validation and output encoding, restricting script execution to non-privileged contexts.
🎯 Exploit Status
Exploitation requires ability to upload favicon files; public proof-of-concept demonstrates the vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
1. Monitor vendor website for updates. 2. Apply patch when available. 3. Test in staging environment before production deployment.
🔧 Temporary Workarounds
Disable Favicon Uploads
allTemporarily disable favicon upload functionality in 66biolinks configuration.
Edit configuration file to remove or comment out favicon upload settings
Implement Input Validation
allAdd server-side validation to reject favicon files containing script tags or malicious content.
Add validation rules in upload handler to check file content for XSS patterns
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block XSS payloads in file uploads
- Restrict favicon uploads to trusted users only and monitor upload activity
🔍 How to Verify
Check if Vulnerable:
Test by uploading a favicon file containing XSS payload (e.g., <script>alert('test')</script>) and check if it executes when viewed.Check Version:
Check 66biolinks admin panel or configuration files for version informationVerify Fix Applied:
After applying fixes, attempt the same XSS payload upload and verify it's either blocked or rendered harmless.📡 Detection & Monitoring
Log Indicators:
- Unusual favicon file uploads
- Large or suspicious favicon files
- Requests containing script tags in file upload parameters
Network Indicators:
- HTTP POST requests to favicon upload endpoints with suspicious content
- Unusual file sizes or types for favicon uploads
SIEM Query:
source="web_server" AND (uri_path="/favicon/upload" OR method="POST") AND (content CONTAINS "<script>" OR file_type="ico" AND size>100KB)