CVE-2025-11976: FuseWP WordPress Plugin CSRF Vulnerability

CVE-2025-11976 Overview

CVE-2025-11976 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the FuseWP WordPress plugin, which synchronizes WordPress users to email marketing platforms including Mailchimp, Constant Contact, and ActiveCampaign. The flaw exists in all plugin versions up to and including 1.1.23.0. The root cause is missing or incorrect nonce validation on the save_changes function within the plugin's sync settings page. Unauthenticated attackers can add or modify sync rules by tricking an authenticated site administrator into clicking a crafted link. Successful exploitation allows manipulation of email marketing sync configurations without administrator consent. The vulnerability is classified under [CWE-352] Cross-Site Request Forgery.

Critical Impact
Unauthenticated attackers can add or edit FuseWP sync rules by tricking administrators into clicking malicious links, potentially redirecting user data flows to attacker-controlled marketing lists.

Affected Products

FuseWP – WordPress User Sync to Email List & Marketing Automation plugin
All versions up to and including 1.1.23.0
WordPress installations integrating FuseWP with Mailchimp, Constant Contact, or ActiveCampaign

Discovery Timeline

2025-10-25 - CVE-2025-11976 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-11976

Vulnerability Analysis

The vulnerability resides in the FuseWP plugin's SyncPage.php file, specifically in the save_changes function responsible for persisting sync rule configurations. The function processes administrative form submissions without properly validating a WordPress nonce token. Nonces are the primary mechanism WordPress uses to defend against CSRF by binding sensitive actions to a specific user session.

Because nonce verification is absent or incorrectly implemented, the plugin cannot distinguish between legitimate administrator requests and forged requests originating from third-party sites. An attacker hosting a malicious page with a crafted form or JavaScript payload can cause an authenticated administrator's browser to submit sync rule changes to the target site.

Exploitation requires user interaction, and the attacker gains no direct access to confidential data. Impact is limited to integrity of the sync rule configuration, which governs how WordPress user data is pushed to external marketing platforms.

Root Cause

The root cause is missing or incorrect nonce validation in the save_changes handler within src/core/src/Admin/SettingsPage/SyncPage.php. WordPress provides check_admin_referer() and wp_verify_nonce() for this purpose, but the vulnerable code path fails to enforce these checks before mutating persistent sync configuration.

Attack Vector

An attacker crafts an HTML page containing a form or JavaScript that submits a POST request to the vulnerable FuseWP admin endpoint. The attacker delivers the link through phishing, social media, or a compromised site. When an authenticated WordPress administrator visits the attacker's page, their browser transmits authenticated session cookies alongside the forged request. The plugin accepts the request and modifies sync rules. See the Wordfence Vulnerability Report and the WordPress Changeset Update for the code-level fix.

Detection Methods for CVE-2025-11976

Indicators of Compromise

Unexpected modifications to FuseWP sync rules in the WordPress admin dashboard
POST requests to FuseWP sync settings endpoints originating from external HTTP Referer headers
New or altered mappings between WordPress user roles and external email list identifiers
Administrator sessions submitting configuration changes shortly after clicking external links

Detection Strategies

Review web server access logs for POST requests to FuseWP admin pages with cross-origin Referer values
Audit the WordPress options table for unexpected changes to FuseWP sync rule entries
Monitor WordPress admin activity logs for sync rule modifications outside change windows
Compare current FuseWP configuration against known-good baselines on a regular schedule

Monitoring Recommendations

Enable a WordPress activity logging plugin to record all administrative configuration changes
Forward web server and WordPress audit logs to a centralized SIEM for correlation
Alert on FuseWP configuration changes that occur without corresponding legitimate admin authentication events
Track outbound sync traffic to Mailchimp, Constant Contact, and ActiveCampaign for anomalous volume or destination lists

How to Mitigate CVE-2025-11976

Immediate Actions Required

Update the FuseWP plugin to a version later than 1.1.23.0 that includes the nonce validation fix
Audit current FuseWP sync rules and revert any unauthorized modifications
Instruct administrators to log out of WordPress sessions before browsing untrusted sites
Rotate API keys used by FuseWP to connect to Mailchimp, Constant Contact, and ActiveCampaign if tampering is suspected

Patch Information

The vendor addressed the vulnerability by adding nonce validation to the save_changes function in SyncPage.php. Refer to the WordPress Changeset Update for the exact code changes and upgrade to the fixed release available through the WordPress plugin repository.

Workarounds

Deactivate the FuseWP plugin until the patched version is installed
Restrict WordPress admin panel access by IP address using web server or firewall rules
Require administrators to use dedicated browsers or profiles for WordPress management to reduce CSRF exposure
Deploy a web application firewall rule that blocks POST requests to FuseWP settings endpoints lacking a same-origin Referer header

bash

# Example WAF rule concept: block cross-origin POSTs to FuseWP admin endpoints
# Adapt syntax to your WAF (ModSecurity, Cloudflare, etc.)
SecRule REQUEST_METHOD "@streq POST" \
  "chain,deny,status:403,id:1011976,msg:'CVE-2025-11976 FuseWP CSRF block'"
  SecRule REQUEST_URI "@contains fusewp" "chain"
  SecRule REQUEST_HEADERS:Referer "!@beginsWith https://your-wordpress-site.example"