CVE-2021-34637
📋 TL;DR
This vulnerability in the Post Index WordPress plugin allows attackers to perform Cross-Site Request Forgery (CSRF) attacks, enabling them to inject malicious scripts into the plugin's settings page. It affects WordPress sites using the plugin up to version 0.7.5, potentially compromising site integrity and user data.
💻 Affected Systems
- Post Index WordPress plugin
📦 What is this software?
Post Index by Post Index Project
⚠️ Risk & Real-World Impact
Worst Case
Attackers could inject persistent malicious scripts, leading to site defacement, data theft, or malware distribution to visitors.
Likely Case
Attackers trick authenticated administrators into executing actions that modify plugin settings with malicious scripts, causing limited site disruption.
If Mitigated
With CSRF protections like nonce tokens, the attack is prevented, maintaining normal plugin functionality.
🎯 Exploit Status
Exploitation involves crafting CSRF payloads; public references and PoCs are available, making it accessible to attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 0.7.5 (check for updates)
Vendor Advisory: https://plugins.trac.wordpress.org/browser/post-index/trunk/php/settings.php
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins > Installed Plugins. 3. Find Post Index plugin and click 'Update Now' if available. 4. Alternatively, delete and reinstall the latest version from the WordPress repository.
🔧 Temporary Workarounds
Disable Post Index Plugin
allTemporarily deactivate the plugin to prevent exploitation until patched.
wp plugin deactivate post-index
Implement CSRF Protection
allAdd nonce verification to the plugin's settings.php file manually if skilled.
🧯 If You Can't Patch
- Restrict access to the WordPress admin panel to trusted IP addresses only.
- Use a web application firewall (WAF) to block CSRF attempts and script injection patterns.
🔍 How to Verify
Check if Vulnerable:
Check the plugin version in WordPress admin under Plugins > Installed Plugins; if version is 0.7.5 or lower, it is vulnerable.Check Version:
wp plugin get post-index --field=versionVerify Fix Applied:
After updating, confirm the plugin version is above 0.7.5 and test the settings page for CSRF vulnerabilities.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /wp-admin/admin.php?page=post-index with script tags or parameters.
Network Indicators:
- HTTP traffic containing CSRF payloads targeting the plugin's settings endpoint.
SIEM Query:
source="wordpress.log" AND (url="/wp-admin/admin.php?page=post-index" AND method="POST" AND (body CONTAINS "<script>" OR body CONTAINS "javascript:"))