CVE-2025-9816: WP Statistics Plugin XSS Vulnerability

CVE-2025-9816 Overview

CVE-2025-9816 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the WP Statistics plugin for WordPress, one of the most popular privacy-friendly analytics plugins in the WordPress ecosystem. The vulnerability exists in all versions up to and including 14.5.4 due to insufficient input sanitization and output escaping of the User-Agent header.

This security flaw allows unauthenticated attackers to inject arbitrary JavaScript code that gets stored in the WordPress database and executes whenever an authenticated user, particularly administrators, views analytics pages containing the malicious data. The attack requires no authentication, making it particularly dangerous for WordPress sites running vulnerable versions.

Critical Impact

Unauthenticated attackers can inject malicious scripts via User-Agent headers that execute in administrator contexts, potentially leading to site takeover, data theft, or malware distribution.

Affected Products

• WP Statistics Plugin versions up to and including 14.5.4
• WordPress sites running vulnerable WP Statistics versions
• All WordPress installations with affected plugin versions regardless of WordPress core version

Discovery Timeline

• 2025-09-27 - CVE CVE-2025-9816 published to NVD
• 2025-09-29 - Last updated in NVD database

Technical Details for CVE-2025-9816

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability stems from the plugin's failure to properly sanitize and escape User-Agent header data before storing it in the database and rendering it in admin dashboard pages. When visitors access a WordPress site, the WP Statistics plugin logs various analytics data including the User-Agent string. An attacker can craft a malicious HTTP request with JavaScript payload embedded in the User-Agent header.

The vulnerable code path can be traced to the devices/models template file where User-Agent data is displayed without proper output escaping. When an administrator views the devices or models statistics page, the stored malicious payload executes in their browser context with full administrative privileges.

The attack is particularly impactful because it targets the administrative interface and requires no prior authentication. Any site visitor can inject malicious scripts that will later execute when administrators review their analytics data.

Root Cause

The root cause is a classic CWE-79 (Improper Neutralization of Input During Web Page Generation) vulnerability. The plugin accepts User-Agent header data from HTTP requests and stores it directly in the database without proper sanitization. When this data is later retrieved and displayed in the admin panel, it is rendered without adequate output escaping, allowing embedded JavaScript to execute.

The vulnerable component appears to be in the template file at includes/admin/templates/pages/devices/models.php where User-Agent derived data is output to the page. The lack of WordPress escaping functions like esc_html() or esc_attr() on untrusted data enables the XSS condition.

Attack Vector

The attack vector is network-based and requires no authentication. An attacker can exploit this vulnerability by:

1. Sending HTTP requests to the target WordPress site with crafted User-Agent headers containing JavaScript payloads
2. The malicious User-Agent data gets logged by WP Statistics into the WordPress database
3. When an administrator navigates to the statistics pages (particularly the devices/models view), the stored script executes
4. The attacker's JavaScript runs with the administrator's session privileges, enabling session hijacking, privilege escalation, or arbitrary actions

The vulnerability does not require user interaction beyond normal administrator activity of reviewing site analytics. Since User-Agent headers are typically not visible to users, this attack can be difficult to detect without proper security monitoring.

Technical details about the specific vulnerable code path can be found in the WordPress Plugin File Reference.

Detection Methods for CVE-2025-9816

Indicators of Compromise

• Unusual or malformed User-Agent strings in web server access logs containing JavaScript code or HTML tags
• Unexpected administrator account creation or privilege changes
• Reports of unexpected behavior when viewing WP Statistics dashboard pages
• Browser console errors or unexpected script execution warnings in the WordPress admin area

Detection Strategies

• Monitor web server logs for User-Agent headers containing suspicious patterns such as <script>, javascript:, onerror=, or other XSS indicators
• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in HTTP headers
• Audit WordPress database tables associated with WP Statistics for stored malicious content
• Enable Content Security Policy (CSP) headers to help mitigate the impact of XSS attacks

Monitoring Recommendations

• Configure real-time alerting for anomalous User-Agent patterns in HTTP request logs
• Monitor WordPress admin user activity for unauthorized actions following statistics page access
• Implement database query logging to detect suspicious data patterns in analytics tables
• Review WP Statistics plugin logs for unusual visitor patterns or high volumes of requests with identical malformed User-Agent strings

How to Mitigate CVE-2025-9816

Immediate Actions Required

• Update WP Statistics plugin to a version newer than 14.5.4 immediately
• Audit existing analytics data for potentially malicious stored content
• Review WordPress administrator accounts for unauthorized changes
• Consider temporarily disabling WP Statistics until the update can be applied if immediate patching is not possible

Patch Information

WordPress site administrators should update the WP Statistics plugin through the WordPress admin dashboard or manually download the latest secure version from the WordPress plugin repository. The patch addresses the vulnerability by implementing proper input sanitization and output escaping for User-Agent header data.

For detailed vulnerability information, refer to the Wordfence Vulnerability Report.

Workarounds

• Implement a Web Application Firewall rule to strip or sanitize suspicious characters from User-Agent headers before they reach WordPress
• Add server-level filtering to reject requests with User-Agent headers containing HTML or JavaScript patterns
• Restrict access to WP Statistics admin pages to specific IP addresses or require additional authentication
• Consider using an alternative analytics solution until the plugin can be safely updated

# Example Apache mod_rewrite rule to block suspicious User-Agent patterns
# Add to .htaccess file in WordPress root directory
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} (<script|javascript:|onerror=|onclick=) [NC]
RewriteRule .* - [F,L]