CVE-2025-39576: WPAdverts WordPress Plugin XSS Vulnerability

CVE-2025-39576 Overview

CVE-2025-39576 is a stored Cross-Site Scripting (XSS) vulnerability affecting the WPAdverts plugin for WordPress, developed by Greg Winiarski. The flaw stems from improper neutralization of user-supplied input during web page generation [CWE-79]. Attackers with low-privilege authenticated access can inject malicious JavaScript that persists in the application and executes in the browsers of other users who view the affected pages. All versions of WPAdverts up to and including 2.2.1 are affected. Successful exploitation requires user interaction, but the scope-changing nature of the vulnerability allows the injected payload to affect resources beyond the initially vulnerable component.

Critical Impact
Authenticated attackers can inject persistent JavaScript payloads that execute in visitors' and administrators' browsers, enabling session hijacking, credential theft, and unauthorized actions on behalf of victims.

Affected Products

WPAdverts plugin for WordPress, all versions up to and including 2.2.1
WordPress sites running WPAdverts with classified listing functionality exposed to authenticated users
Any deployment where low-privilege accounts can submit content processed by WPAdverts

Discovery Timeline

2025-04-16 - CVE-2025-39576 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-39576

Vulnerability Analysis

The WPAdverts plugin fails to sanitize user-controlled input before rendering it within generated web pages. This omission allows attackers to embed HTML and JavaScript inside fields that are later reflected to other users. Because the payload persists in the WordPress database, every subsequent page load containing the tainted data triggers script execution in the viewer's browser.

The vulnerability requires an authenticated session with low privileges, which lowers the barrier for exploitation on sites that allow user registration or advertiser accounts. Victim interaction with the injected page completes the attack chain. The scope change indicator means the injected script executes in a security context different from the vulnerable component, allowing lateral impact against administrative sessions.

Root Cause

The root cause is the absence of proper output encoding and input sanitization on fields processed by WPAdverts. The plugin trusts values submitted through advert creation or editing flows and writes them into HTML output without escaping HTML entities or filtering script constructs. This aligns directly with the [CWE-79] pattern of improper neutralization during web page generation.

Attack Vector

An attacker registers or authenticates as a low-privilege user permitted to submit adverts. The attacker crafts an advert containing a JavaScript payload inside a vulnerable field. When a site visitor, moderator, or administrator loads the advert, the browser parses and executes the payload in the site's origin. Consult the Patchstack XSS Vulnerability Advisory for additional technical context.

No public exploit code is currently referenced for this CVE, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS score is 0.305%.

Detection Methods for CVE-2025-39576

Indicators of Compromise

Advert entries in the WordPress database containing <script>, onerror=, onload=, or javascript: constructs within text fields
Unexpected outbound requests from administrator browsers to attacker-controlled domains after viewing advert pages
Newly created administrator accounts or modified user roles following advert moderation activity
Session cookies appearing in web server referer logs or third-party analytics platforms

Detection Strategies

Query the WordPress wp_posts and WPAdverts custom tables for HTML tags and JavaScript event handlers in user-submitted fields
Deploy a Web Application Firewall (WAF) rule set to inspect POST parameters submitted to WPAdverts endpoints for XSS signatures
Enable Content Security Policy (CSP) reporting to capture inline script violations originating from advert pages
Correlate low-privilege account creation with subsequent advert submissions containing suspicious markup

Monitoring Recommendations

Log and review all authenticated advert submissions, including field-level content, for automated review
Monitor administrative session activity following advert moderation for anomalous API calls or role changes
Alert on failed CSP directives referencing the WPAdverts URL paths
Track plugin version inventory across managed WordPress sites to identify hosts running vulnerable releases

How to Mitigate CVE-2025-39576

Immediate Actions Required

Identify all WordPress installations running WPAdverts 2.2.1 or earlier and prioritize them for patching
Restrict advert submission privileges to trusted users until a fixed version is deployed
Review existing advert content for stored payloads and purge malicious entries from the database
Force session invalidation for administrator accounts that may have viewed tampered advert pages

Patch Information

At the time of publication, the advisory records the vulnerability as affecting WPAdverts through version 2.2.1. Administrators should monitor the Patchstack XSS Vulnerability Advisory and the plugin's official WordPress.org listing for a fixed release, and apply the update as soon as it becomes available.

Workarounds

Deploy a WAF rule blocking HTML tags and JavaScript event handlers in POST parameters targeting WPAdverts submission endpoints
Implement a strict Content Security Policy that disallows inline scripts on pages rendering WPAdverts content
Disable public advert submissions and require manual administrator entry until the plugin is patched
Temporarily deactivate the WPAdverts plugin on sites where classified functionality is not business-critical

bash

# Example Content Security Policy header to limit inline script execution
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'"