CVE-2025-67991: User Extra Fields XSS Vulnerability

CVE-2025-67991 Overview

CVE-2025-67991 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the WordPress User Extra Fields plugin (wp-user-extra-fields) developed by vanquish. The vulnerability stems from improper neutralization of input during web page generation, allowing attackers to inject malicious scripts that execute in the context of a victim's browser session.

Critical Impact

This Reflected XSS vulnerability allows attackers to execute arbitrary JavaScript in authenticated user sessions, potentially leading to session hijacking, credential theft, and unauthorized actions on behalf of the victim.

Affected Products

• WordPress User Extra Fields plugin versions through 16.8
• All WordPress installations running vulnerable versions of wp-user-extra-fields
• Users interacting with maliciously crafted links targeting vulnerable plugin endpoints

Discovery Timeline

• 2026-02-20 - CVE-2025-67991 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2025-67991

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). The User Extra Fields plugin fails to properly sanitize user-supplied input before reflecting it back in the HTTP response, creating an opportunity for Reflected XSS attacks.

In a Reflected XSS scenario, the malicious payload is delivered via a specially crafted URL or request parameter. When a victim clicks on the malicious link, the unsanitized input is processed by the vulnerable plugin and reflected directly into the page output without proper encoding or escaping. The browser then executes the injected script in the context of the WordPress site's origin.

The attack requires user interaction (clicking a malicious link), but successful exploitation can lead to confidentiality, integrity, and availability impacts. Attackers can steal session cookies, modify page content, redirect users to phishing sites, or perform actions as the authenticated user.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding within the User Extra Fields plugin. The plugin fails to implement proper sanitization mechanisms for user-controlled data before including it in dynamically generated web pages. WordPress provides built-in sanitization functions such as esc_html(), esc_attr(), and wp_kses() that should be applied to all user input, but these protections were not adequately implemented in the affected code paths.

Attack Vector

The attack vector is network-based, requiring an attacker to craft a malicious URL containing the XSS payload and deliver it to a potential victim. Attack scenarios include:

1. Phishing Campaigns: Attackers distribute malicious links via email or social media targeting WordPress administrators
2. Watering Hole Attacks: Embedding malicious links on compromised websites frequented by WordPress users
3. Social Engineering: Convincing users to click links through deceptive messaging

When the victim visits the malicious URL while authenticated to the WordPress site, the injected script executes with the victim's privileges. This can facilitate session hijacking, administrative account takeover, or deployment of additional malware.

The vulnerability affects the plugin's handling of user input in web page generation. For detailed technical analysis, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-67991

Indicators of Compromise

• Unusual URL parameters containing JavaScript code or HTML tags in requests to WordPress plugin endpoints
• Web server logs showing requests with encoded script payloads (%3Cscript%3E, javascript:, onerror=)
• User reports of unexpected behavior or redirects when interacting with the User Extra Fields plugin
• Browser console errors indicating blocked inline scripts (if CSP is configured)

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS payload patterns in request parameters
• Monitor web server access logs for suspicious URL patterns containing script tags or event handlers
• Deploy browser-based XSS detection using Content Security Policy violation reporting
• Utilize WordPress security plugins that scan for vulnerable plugin versions and suspicious activity

Monitoring Recommendations

• Enable detailed logging for all requests to wp-user-extra-fields plugin endpoints
• Configure alerting for any CSP violation reports originating from WordPress pages
• Regularly audit installed WordPress plugins against known vulnerability databases
• Monitor for anomalous user session behavior that may indicate session hijacking

How to Mitigate CVE-2025-67991

Immediate Actions Required

• Update the User Extra Fields plugin to a patched version if available from the vendor
• If no patch is available, consider temporarily deactivating the wp-user-extra-fields plugin until a fix is released
• Implement Content Security Policy (CSP) headers to mitigate the impact of XSS attacks
• Review WordPress user accounts for any unauthorized changes or suspicious activity

Patch Information

Organizations should monitor the Patchstack Vulnerability Report for updates on patch availability. Until a patch is released, implement the workarounds described below to reduce risk exposure. Verify the installed plugin version by navigating to the WordPress admin panel under Plugins and checking the version number for User Extra Fields.

Workarounds

• Implement a Web Application Firewall with XSS filtering rules to block malicious payloads before they reach the application
• Add Content Security Policy headers to restrict inline script execution: Content-Security-Policy: script-src 'self'
• Restrict access to the WordPress admin panel to trusted IP addresses only
• Educate users about phishing risks and the importance of not clicking untrusted links

# Apache .htaccess CSP configuration
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';"
    Header set X-XSS-Protection "1; mode=block"
    Header set X-Content-Type-Options "nosniff"
</IfModule>