CVE-2025-31440: Terms of Use Plugin CSRF Vulnerability

CVE-2025-31440 Overview

CVE-2025-31440 is a Cross-Site Request Forgery (CSRF) vulnerability in the Strategy11 Team Terms of Use WordPress plugin (terms-of-use-2). The flaw allows an attacker to chain CSRF with Stored Cross-Site Scripting (XSS), persisting attacker-controlled script in the plugin's stored data. The issue affects all versions of the Terms of Use plugin up to and including version 2.0. The vulnerability is tracked under CWE-352: Cross-Site Request Forgery.

Critical Impact

An attacker who tricks an authenticated administrator into visiting a malicious page can forge requests that inject persistent JavaScript into plugin-managed content, leading to session theft, account takeover, and further compromise of WordPress sites.

Affected Products

• Strategy11 Team Terms of Use plugin (terms-of-use-2) for WordPress
• All versions from n/a through <= 2.0
• WordPress sites with the affected plugin installed and active

Discovery Timeline

• 2025-03-28 - CVE-2025-31440 published to the National Vulnerability Database (NVD)
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-31440

Vulnerability Analysis

The Terms of Use plugin exposes one or more state-changing endpoints that do not validate request authenticity. The endpoints lack CSRF protection such as WordPress nonce verification through wp_verify_nonce() or check_admin_referer(). An attacker who hosts a crafted page can submit a forged POST request that executes under the privileges of an authenticated administrator who visits the page.

Because the affected handler also fails to sanitize or escape user-supplied input before storing it, the forged request writes attacker-controlled HTML or JavaScript into plugin storage. The payload is later rendered in the WordPress admin or front-end context, producing a Stored XSS condition. The attack requires user interaction (UI:R) and changes scope (S:C) because the injected script executes in a different security context than the vulnerable endpoint.

Root Cause

The root cause is missing CSRF token validation on plugin actions combined with insufficient output encoding of stored values. Both controls are required, and the absence of either is enough to enable the chain. WordPress provides nonce APIs precisely to defeat CSRF, and the affected plugin does not enforce them on the vulnerable handler.

Attack Vector

An attacker crafts an HTML page containing a hidden form or fetch() request that targets the plugin's administrative endpoint with an XSS payload as a parameter value. The attacker then lures a logged-in WordPress administrator to that page through phishing, a forum post, or a malicious advertisement. The browser submits the request with the administrator's session cookies, and the plugin stores the payload. Any subsequent page render that outputs the stored value triggers script execution in the victim's browser. Refer to the Patchstack WordPress Vulnerability Report for additional technical detail.

Detection Methods for CVE-2025-31440

Indicators of Compromise

• Unexpected <script> tags, event handlers (onerror, onload), or obfuscated JavaScript in plugin-managed Terms of Use content stored in wp_options or related tables.
• POST requests to plugin admin endpoints originating from an HTTP Referer header outside the site's own admin domain.
• New or modified WordPress administrator accounts and unexpected plugin or theme installations following admin browsing activity.

Detection Strategies

• Audit the WordPress database for stored plugin values containing HTML tags, JavaScript URI schemes, or encoded script payloads.
• Inspect web server access logs for POST requests to terms-of-use-2 endpoints lacking valid nonce parameters or with off-site referrers.
• Deploy a Web Application Firewall (WAF) rule that flags requests targeting the plugin's admin actions without a matching _wpnonce parameter.

Monitoring Recommendations

• Enable WordPress activity logging to record plugin setting changes, with alerts for modifications outside normal change windows.
• Monitor outbound network calls from administrator browsers to unfamiliar domains, which can indicate XSS payload execution.
• Track file integrity for the active theme and wp-content directories to catch follow-on persistence introduced via stolen admin sessions.

How to Mitigate CVE-2025-31440

Immediate Actions Required

• Update the Terms of Use plugin to a version higher than 2.0 once the vendor releases a patched build.
• If no fixed version is available, deactivate and remove the terms-of-use-2 plugin from all affected WordPress installations.
• Force a password reset and re-issue session tokens for all WordPress administrator accounts that may have visited untrusted pages while authenticated.

Patch Information

At the time of publication, the Patchstack advisory lists the vulnerability as affecting versions up to and including 2.0. Administrators should consult the plugin's WordPress.org page for the latest release notes and apply the vendor-supplied patch as soon as it is published.

Workarounds

• Restrict access to /wp-admin/ by source IP using web server or WAF rules so that CSRF-baiting pages cannot reach the vulnerable endpoint with admin cookies.
• Require administrators to use a dedicated browser profile for WordPress management to prevent cross-context request forgery from general browsing sessions.
• Add a virtual patch at the WAF that rejects POST requests to plugin endpoints when the _wpnonce parameter is missing or the Referer header does not match the site origin.

# Example WAF rule (ModSecurity) to block CSRF attempts against the plugin
SecRule REQUEST_URI "@contains /wp-admin/admin.php" \
  "chain,phase:2,deny,status:403,id:1003144,\
  msg:'CVE-2025-31440: missing nonce on terms-of-use-2 request'"
  SecRule ARGS:page "@streq terms-of-use-2" "chain"
    SecRule &ARGS:_wpnonce "@eq 0"