CVE-2025-31395 Overview
CVE-2025-31395 is a Cross-Site Request Forgery (CSRF) vulnerability in the Easy Custom CSS WordPress plugin developed by a.ankit. The flaw affects all plugin versions up to and including 1.0. An attacker can exploit the missing CSRF protection to trick an authenticated administrator into submitting a forged request that injects persistent JavaScript into the site's custom CSS settings. The chained outcome is Stored Cross-Site Scripting (XSS), which executes in the browser of any visitor who loads an affected page. The weakness is tracked under CWE-352: Cross-Site Request Forgery.
Critical Impact
A successful attack chains CSRF with Stored XSS, allowing arbitrary script execution against site visitors and administrators, including session theft and content manipulation.
Affected Products
- Easy Custom CSS WordPress plugin (slug: easy-custom-css)
- All versions from n/a through 1.0
- WordPress sites with an authenticated administrator session susceptible to CSRF
Discovery Timeline
- 2025-04-09 - CVE-2025-31395 published to NVD
- 2026-04-23 - Last updated in NVD database
Technical Details for CVE-2025-31395
Vulnerability Analysis
The Easy Custom CSS plugin exposes an administrative function that saves user-supplied CSS content to the WordPress database. The handler does not verify a valid WordPress nonce or other anti-CSRF token before persisting the submitted data. An attacker who lures an authenticated administrator into visiting a malicious page can cause the browser to issue a state-changing request against the plugin's settings endpoint. Because the administrator's session cookies are sent automatically, the request is processed with full privileges.
The submitted CSS field is stored without adequate output encoding, enabling injection of HTML and JavaScript payloads via <style> context breakouts or </style><script> sequences. The malicious script is then served to any user visiting a page that renders the custom CSS, producing Stored XSS in the [Scope: Changed] context reflected by the CVSS vector.
Root Cause
The root cause is the absence of CSRF token validation on the plugin's settings save handler, compounded by insufficient sanitization of the stored CSS payload. WordPress provides check_admin_referer() and wp_nonce_field() helpers for this exact protection, but the affected versions do not invoke them on the vulnerable code path.
Attack Vector
The attack requires an authenticated WordPress administrator to load an attacker-controlled page or click a crafted link. The malicious page issues an auto-submitting form or fetch request to the plugin's settings endpoint containing the XSS payload in the CSS field. User interaction is required, consistent with the UI:R component of the CVSS vector. Once stored, the payload executes for every subsequent page view that includes the custom CSS output, turning a one-time CSRF into a persistent XSS foothold.
No public proof-of-concept exploit code is available. See the Patchstack WordPress Vulnerability Report for additional advisory details.
Detection Methods for CVE-2025-31395
Indicators of Compromise
- Unexpected <script>, javascript:, or event-handler strings inside the plugin's stored custom CSS option in the wp_options table.
- Outbound requests from site visitors to unfamiliar third-party domains originating after page loads on affected sites.
- Administrator account activity that includes plugin settings updates without a corresponding authenticated admin UI session in access logs.
Detection Strategies
- Inspect WordPress database rows associated with easy-custom-css for HTML tags or JavaScript keywords that should not appear in a CSS field.
- Review web server access logs for POST requests to plugin admin endpoints lacking a same-origin Referer header.
- Scan rendered front-end pages for injected <script> tags emitted by the plugin's CSS output handler.
Monitoring Recommendations
- Alert on modifications to plugin option rows outside of approved change windows.
- Monitor administrator browser sessions for cross-origin POST requests to /wp-admin/admin.php and /wp-admin/options.php.
- Track new outbound network connections from end-user browsers loading WordPress pages that host the plugin.
How to Mitigate CVE-2025-31395
Immediate Actions Required
- Deactivate and remove the Easy Custom CSS plugin until a patched release is published by the maintainer.
- Audit the plugin's stored CSS settings and remove any content containing HTML or script payloads.
- Force a password reset and session invalidation for all administrator accounts on affected sites.
Patch Information
No fixed version has been published at the time of writing. The vulnerability affects all versions through 1.0. Site operators should track the Patchstack advisory for an upstream fix and apply it when released.
Workarounds
- Replace Easy Custom CSS with a maintained alternative such as the WordPress core Additional CSS feature in the Customizer.
- Restrict administrator access using IP allowlists on /wp-admin/ to reduce CSRF exposure from arbitrary external pages.
- Deploy a web application firewall rule that blocks cross-origin POSTs to plugin admin endpoints lacking a valid Referer and nonce.
- Enforce a strict Content Security Policy (CSP) that disallows inline scripts on front-end pages to limit Stored XSS execution.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
