CVE-2021-39353
📋 TL;DR
This vulnerability allows attackers to perform Cross-Site Request Forgery (CSRF) attacks against WordPress sites using the Easy Registration Forms plugin. Attackers can trick authenticated administrators into executing malicious actions, potentially injecting arbitrary web scripts. Sites running the plugin version 2.1.1 or earlier are affected.
💻 Affected Systems
- Easy Registration Forms WordPress Plugin
📦 What is this software?
Easy Registration Forms by Easyregistrationforms
⚠️ Risk & Real-World Impact
Worst Case
Complete site takeover through script injection leading to data theft, defacement, or malware distribution.
Likely Case
Unauthorized form creation/modification, script injection in forms, or administrative actions performed without consent.
If Mitigated
No impact if proper CSRF protections are implemented or plugin is updated/disabled.
🎯 Exploit Status
Exploitation requires social engineering to trick authenticated users. CSRF attacks are well-understood and tools exist.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.1.2 or later
Vendor Advisory: https://plugins.trac.wordpress.org/changeset/2608228/easy-registration-forms
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins > Installed Plugins. 3. Find 'Easy Registration Forms'. 4. Click 'Update Now' if available. 5. Alternatively, download latest version from WordPress repository and replace plugin files.
🔧 Temporary Workarounds
Disable Plugin
allTemporarily disable the vulnerable plugin until patched.
wp plugin deactivate easy-registration-forms
Add CSRF Protection Manually
allAdd nonce validation to ajax_add_form function in class-form.php
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers
- Use web application firewall with CSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check plugin version in WordPress admin under Plugins > Installed Plugins. Version 2.1.1 or earlier is vulnerable.Check Version:
wp plugin get easy-registration-forms --field=versionVerify Fix Applied:
Verify plugin version is 2.1.2 or later. Check that nonce validation exists in includes/class-form.php around line 256.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to admin-ajax.php with action=ajax_add_form
- Multiple form creation/modification events from single user session
Network Indicators:
- CSRF attack patterns in web traffic
- Unexpected cross-origin requests to WordPress admin endpoints
SIEM Query:
source="wordpress.log" AND ("ajax_add_form" OR "admin-ajax.php") AND status=200🔗 References
- https://plugins.trac.wordpress.org/browser/easy-registration-forms/tags/2.1.1/includes/class-form.php#L256
- https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39353
- https://plugins.trac.wordpress.org/browser/easy-registration-forms/tags/2.1.1/includes/class-form.php#L256
- https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39353
