CVE-2025-11876
📋 TL;DR
The Mailgun Subscriptions WordPress plugin has a stored XSS vulnerability in its 'mailgun_subscription_form' shortcode. Authenticated attackers with contributor-level access or higher can inject malicious scripts that execute when users view compromised pages. This affects all plugin versions up to and including 1.3.1.
💻 Affected Systems
- Mailgun Subscriptions WordPress Plugin
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal admin credentials, redirect users to malicious sites, deface websites, or install backdoors for persistent access.
Likely Case
Attackers with contributor access inject malicious scripts to steal user session cookies or redirect visitors to phishing pages.
If Mitigated
With proper user role management and content review, impact is limited to defacement or minor data theft from low-privilege users.
🎯 Exploit Status
Exploitation requires authenticated access but is technically simple once attacker has contributor privileges.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 1.3.1
Vendor Advisory: https://plugins.trac.wordpress.org/browser/mailgun-subscriptions/
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins → Installed Plugins. 3. Find Mailgun Subscriptions plugin. 4. Click 'Update Now' if available. 5. If no update available, deactivate and delete plugin, then install latest version from WordPress repository.
🔧 Temporary Workarounds
Remove Contributor Access
allTemporarily remove contributor-level access for untrusted users until patch is applied.
Disable Plugin
linuxDeactivate the Mailgun Subscriptions plugin if not essential.
wp plugin deactivate mailgun-subscriptions
🧯 If You Can't Patch
- Implement strict user role management and review all contributor content before publication
- Deploy web application firewall with XSS protection rules
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin panel → Plugins → Installed Plugins for Mailgun Subscriptions version. If version is 1.3.1 or lower, you are vulnerable.Check Version:
wp plugin get mailgun-subscriptions --field=versionVerify Fix Applied:
After updating, verify plugin version is higher than 1.3.1 in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to WordPress admin-ajax.php with mailgun_subscription_form parameters
- Multiple failed login attempts followed by successful contributor login
Network Indicators:
- Inbound traffic from unusual locations to WordPress admin interface
- Outbound connections to suspicious domains after page views
SIEM Query:
source="wordpress.log" AND ("mailgun_subscription_form" OR "contributor" AND "post")🔗 References
- https://github.com/flightless/mailgun-subscriptions/pull/8/commits/a8b597e3a09f3a1b76436d09de434fd9bfe29f64
- https://plugins.trac.wordpress.org/browser/mailgun-subscriptions/tags/1.2.0/Mailgun_Subscriptions/Subscription_Form.php#L101
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=3413662%40mailgun-subscriptions&new=3413662%40mailgun-subscriptions&sfp_email=&sfph_mail=
- https://www.wordfence.com/threat-intel/vulnerabilities/id/149e60cc-9612-4651-b02d-4b68a3533d36?source=cve
