CVE-2024-3559
📋 TL;DR
The Custom Field Suite WordPress plugin up to version 2.6.7 has a stored XSS vulnerability in the 'cfs[post_content]' parameter. Authenticated attackers with contributor-level access or higher can inject malicious scripts that execute when users view compromised pages. This affects WordPress sites using vulnerable versions of the plugin.
💻 Affected Systems
- Custom Field Suite WordPress Plugin
📦 What is this software?
Custom Field Suite by Custom Field Suite Project
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal admin credentials, deface websites, redirect users to malicious sites, or install backdoors for persistent access.
Likely Case
Attackers with contributor accounts inject malicious scripts to steal user session cookies or perform phishing attacks against site visitors.
If Mitigated
With proper input validation and output escaping, the vulnerability is prevented, though contributor accounts could still be compromised.
🎯 Exploit Status
Exploitation requires authenticated access at contributor level or higher. Public proof-of-concept exists in vulnerability reports.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.6.8
Vendor Advisory: https://plugins.trac.wordpress.org/changeset/3088472/custom-field-suite/trunk/includes/api.php
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins → Installed Plugins. 3. Find Custom Field Suite and click 'Update Now'. 4. Verify version shows 2.6.8 or higher.
🔧 Temporary Workarounds
Disable Plugin
allTemporarily disable the Custom Field Suite plugin until patched
wp plugin deactivate custom-field-suite
Restrict Contributor Access
allTemporarily remove contributor-level user accounts or restrict their permissions
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block XSS payloads in 'cfs[post_content]' parameter
- Enable Content Security Policy (CSP) headers to mitigate script execution
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin panel → Plugins → Installed Plugins → Custom Field Suite version. If version is 2.6.7 or lower, you are vulnerable.Check Version:
wp plugin get custom-field-suite --field=versionVerify Fix Applied:
After updating, verify Custom Field Suite version shows 2.6.8 or higher in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests containing 'cfs[post_content]' parameter with script tags or JavaScript code
- Multiple failed authentication attempts followed by successful contributor login
Network Indicators:
- HTTP requests with suspicious payloads in 'cfs[post_content]' parameter
- Outbound connections to unknown domains after page views
SIEM Query:
SELECT * FROM web_logs WHERE url_parameters LIKE '%cfs%5Bpost_content%5D%' AND (url_parameters LIKE '%script%' OR url_parameters LIKE '%javascript%' OR url_parameters LIKE '%onload%' OR url_parameters LIKE '%onerror%')🔗 References
- https://plugins.trac.wordpress.org/browser/custom-field-suite/trunk/includes/api.php#L282
- https://plugins.trac.wordpress.org/browser/custom-field-suite/trunk/includes/form.php#L69
- https://www.wordfence.com/threat-intel/vulnerabilities/id/56d8af3b-6c00-49ed-872a-64f7bebb470b?source=cve
- https://plugins.trac.wordpress.org/browser/custom-field-suite/trunk/includes/api.php#L282
- https://plugins.trac.wordpress.org/browser/custom-field-suite/trunk/includes/form.php#L69
- https://www.wordfence.com/threat-intel/vulnerabilities/id/56d8af3b-6c00-49ed-872a-64f7bebb470b?source=cve
