CVE-2025-49399: NEX-Forms WordPress Plugin CSRF Vulnerability

CVE-2025-49399 Overview

CVE-2025-49399 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the NEX-Forms WordPress plugin (nex-forms-express-wp-form-builder) developed by Basix. This vulnerability allows attackers to trick authenticated users into performing unintended actions on the WordPress site where the plugin is installed, potentially leading to unauthorized configuration changes or data manipulation.

Critical Impact

Attackers can exploit this CSRF vulnerability to forge malicious requests on behalf of authenticated WordPress administrators, potentially compromising form configurations, accessing submitted data, or modifying plugin settings without proper authorization.

Affected Products

• NEX-Forms WordPress Plugin versions up to and including 9.1.3
• WordPress installations with nex-forms-express-wp-form-builder active

Discovery Timeline

• 2025-08-20 - CVE-2025-49399 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-49399

Vulnerability Analysis

This vulnerability stems from inadequate CSRF token validation within the NEX-Forms plugin. Cross-Site Request Forgery occurs when a web application fails to verify that state-changing requests originate from the legitimate user session. In the context of WordPress plugins, this typically manifests when administrative actions lack proper nonce verification.

The NEX-Forms plugin, which provides form building capabilities for WordPress websites, processes various administrative requests without sufficient validation of request authenticity. This allows an attacker to craft malicious web pages or links that, when visited by an authenticated administrator, execute unauthorized actions within the WordPress admin context.

Root Cause

The root cause of CVE-2025-49399 is the absence or improper implementation of WordPress nonce verification (CWE-352) in one or more administrative functions within the NEX-Forms plugin. WordPress provides built-in CSRF protection through its nonce system (wp_nonce_field(), wp_verify_nonce()), but this vulnerability indicates these security mechanisms were not properly implemented in affected code paths.

Attack Vector

The attack requires social engineering to lure an authenticated WordPress administrator to visit an attacker-controlled web page or click a malicious link. The attack sequence typically follows this pattern:

1. The attacker identifies a vulnerable endpoint in the NEX-Forms plugin that lacks CSRF protection
2. A malicious HTML page is crafted containing a hidden form or JavaScript that submits a forged request
3. The victim (authenticated WordPress admin) is tricked into visiting the attacker's page
4. The victim's browser automatically includes session cookies with the forged request
5. The vulnerable endpoint processes the request as if it were legitimate

The vulnerability can be exploited to perform various actions depending on which plugin functions lack proper CSRF protection, potentially including modifying form configurations, changing plugin settings, or accessing form submission data.

Detection Methods for CVE-2025-49399

Indicators of Compromise

• Unexpected changes to NEX-Forms plugin settings or form configurations
• Suspicious form modifications that administrators did not authorize
• Unusual administrative activity in WordPress logs coinciding with external site visits
• Modified form handler URLs or redirect destinations

Detection Strategies

• Review WordPress admin activity logs for unauthorized NEX-Forms configuration changes
• Monitor for unusual HTTP POST requests to NEX-Forms admin endpoints from external referrers
• Implement Content Security Policy headers to detect potential CSRF attack vectors
• Audit form configurations for unexpected modifications

Monitoring Recommendations

• Enable detailed logging for WordPress admin actions, particularly plugin configuration changes
• Configure web application firewall (WAF) rules to flag requests with suspicious or missing referrer headers
• Monitor for rapid successive administrative actions that may indicate automated CSRF exploitation
• Review access logs for patterns indicating external site referrers triggering admin actions

How to Mitigate CVE-2025-49399

Immediate Actions Required

• Update NEX-Forms plugin to a version newer than 9.1.3 when a patched version becomes available
• Temporarily disable the NEX-Forms plugin if it is not critical to operations until a patch is released
• Implement additional CSRF protection at the web server or WAF level
• Educate WordPress administrators about the risks of clicking unknown links while logged in

Patch Information

Organizations should monitor the Patchstack WordPress Vulnerability Database for updates regarding patched versions of the NEX-Forms plugin. Ensure automatic plugin updates are enabled or establish a process to promptly apply security updates when released by Basix.

Workarounds

• Restrict WordPress admin access to trusted IP addresses using .htaccess or firewall rules
• Use browser extensions that isolate admin sessions or disable automatic cookie sending for cross-origin requests
• Log out of WordPress admin sessions when not actively performing administrative tasks
• Implement SameSite cookie attributes at the WordPress level to prevent cross-origin cookie transmission

# Apache .htaccess configuration to restrict wp-admin access by IP
<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond %{REQUEST_URI} ^/wp-admin [NC]
    RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.100$
    RewriteCond %{REMOTE_ADDR} !^10\.0\.0\.50$
    RewriteRule .* - [F,L]
</IfModule>