CVE-2021-34634
📋 TL;DR
This Cross-Site Request Forgery (CSRF) vulnerability in the Nifty Newsletters WordPress plugin allows attackers to trick authenticated administrators into executing malicious actions without their knowledge. Attackers can inject arbitrary web scripts through the sola_nl_wp_head function, potentially compromising the WordPress site. All WordPress sites using vulnerable versions of the Nifty Newsletters plugin are affected.
💻 Affected Systems
- Nifty Newsletters WordPress Plugin
📦 What is this software?
Sola Newsletters by Sola Newsletters Project
⚠️ Risk & Real-World Impact
Worst Case
Complete site takeover through privilege escalation, data theft, malware injection, or defacement if an admin is tricked into executing malicious requests.
Likely Case
Unauthorized script injection leading to backdoor installation, data exfiltration, or redirection to malicious sites.
If Mitigated
Limited impact with proper CSRF protections, admin awareness training, and network segmentation in place.
🎯 Exploit Status
Exploitation requires social engineering to trick authenticated users. CSRF attacks are well-understood and tools exist to automate them.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 4.0.24 or later
Vendor Advisory: https://plugins.trac.wordpress.org/browser/sola-newsletters/trunk/sola-newsletters.php
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins > Installed Plugins. 3. Find 'Nifty Newsletters' and check if update is available. 4. Click 'Update Now' or manually update to version 4.0.24+. 5. Verify plugin functionality after update.
🔧 Temporary Workarounds
Disable Plugin
allTemporarily disable the Nifty Newsletters plugin until patched
wp plugin deactivate sola-newsletters
Implement CSRF Protection
allAdd WordPress nonce verification to plugin functions
Manual code modification required - add wp_nonce_field and wp_verify_nonce checks
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers to limit script execution
- Use web application firewall (WAF) rules to block CSRF attempts and suspicious requests
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin panel > Plugins > Installed Plugins for Nifty Newsletters version. If version is 4.0.23 or lower, you are vulnerable.Check Version:
wp plugin get sola-newsletters --field=versionVerify Fix Applied:
After updating, verify plugin version shows 4.0.24 or higher in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to sola-newsletters.php
- Multiple failed CSRF token validations
- Unexpected script injection in newsletter content
Network Indicators:
- Suspicious cross-origin requests to WordPress admin endpoints
- Unexpected iframe or form submissions
SIEM Query:
source="wordpress" AND (uri="/wp-admin/admin-ajax.php" OR uri CONTAINS "sola-newsletters") AND method="POST" AND NOT referer CONTAINS own_domain🔗 References
- https://plugins.trac.wordpress.org/browser/sola-newsletters/trunk/sola-newsletters.php#L774
- https://www.wordfence.com/vulnerability-advisories/#CVE-2021-34634
- https://plugins.trac.wordpress.org/browser/sola-newsletters/trunk/sola-newsletters.php#L774
- https://www.wordfence.com/vulnerability-advisories/#CVE-2021-34634
