CVE-2025-39351

Executive Summary

CVE-2025-39351 identifies a Cross-Site Request Forgery (CSRF) vulnerability in the Themegoods Grand Restaurant WordPress theme, affecting versions up to and including 7.0. This vulnerability allows an attacker to trick an authenticated administrator into performing unintended actions, such as modifying theme settings or injecting malicious content, without their consent. The attack requires user interaction (clicking a crafted link) and has a CVSS score of 4.3 (Medium). As this is a WordPress theme vulnerability, it falls within the WordPress ecosystem and does not implicate Apache or Nginx. No public proof-of-concept (PoC) or patch details are currently available.

Supply Chain & Package Security

This vulnerability affects a commercial WordPress theme distributed via Themegoods. Since it is not an open-source package (NPM, PyPI, Go, Ruby), supply chain risks are limited to the theme’s update mechanism and the integrity of the vendor’s distribution channel. Users should verify the authenticity of theme updates and ensure they are obtained directly from the vendor.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector (AV): Network – The attack can be launched remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – The attacker does not need prior authentication.
• User Interaction (UI): Required – The victim must click a malicious link or visit a crafted page.
• Scope (S): Unchanged – The vulnerable component and the attacker’s scope are the same.
• Confidentiality (C): None – No data is exposed.
• Integrity (I): Low – The attacker can modify settings or content but not all data.
• Availability (A): None – No denial-of-service impact.

Threat Level: Medium. Exploitation requires social engineering, but the impact on integrity could lead to defacement or unauthorized configuration changes.

Deep Dive & Mechanics

The vulnerability resides in the Grand Restaurant WordPress theme’s administrative functions. CSRF occurs because the theme does not implement proper anti-CSRF tokens (nonces) in its admin AJAX handlers or form submissions. An attacker can craft a malicious HTML page that, when visited by an authenticated administrator, triggers a state-changing request to the WordPress admin area (e.g., /wp-admin/admin-ajax.php or a theme-specific endpoint). Since the victim’s browser automatically includes their session cookies, the request is processed as if initiated by the administrator.

Common attack vectors include:

• Changing theme options (e.g., restaurant menu items, contact details).
• Injecting malicious JavaScript into theme settings (stored XSS).
• Modifying user roles or permissions if the theme exposes such functionality.

The lack of a nonce check in the theme’s code allows these cross-origin requests to succeed.

Vulnerable vs. Patched Code

Vulnerable Code (Example): In the theme’s functions.php or AJAX handler file, a typical vulnerable pattern might look like:

add_action('wp_ajax_grandrestaurant_update_settings', 'grandrestaurant_update_settings');
function grandrestaurant_update_settings() {
    // No nonce verification
    update_option('grandrestaurant_menu_items', $_POST['menu_items']);
    wp_die();
}

Patched Code (Hypothetical): A secure version would include a nonce check:

add_action('wp_ajax_grandrestaurant_update_settings', 'grandrestaurant_update_settings');
function grandrestaurant_update_settings() {
    // Verify nonce
    if (!wp_verify_nonce($_POST['_wpnonce'], 'grandrestaurant_settings_nonce')) {
        wp_die('CSRF validation failed.');
    }
    update_option('grandrestaurant_menu_items', sanitize_text_field($_POST['menu_items']));
    wp_die();
}

Since no official patch is available, users must manually add nonce checks or wait for a vendor update.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• A WordPress site running Grand Restaurant theme <= 7.0.
• An authenticated administrator session (victim).

Exploit Steps:

1. Craft a malicious HTML page that submits a form to the vulnerable endpoint.
2. Host the page on an attacker-controlled server or use a phishing email.
3. Lure the victim to visit the page while logged into WordPress.

Example HTML Payload:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST" id="csrf_form">
    <input type="hidden" name="action" value="grandrestaurant_update_settings">
    <input type="hidden" name="menu_items" value="Malicious Menu Item">
    <input type="submit" value="Click me">
</form>
<script>document.getElementById('csrf_form').submit();</script>
</body>
</html>

Expected Outcome: The victim’s browser sends the request with their cookies, and the theme settings are altered.

Blue Team (Defense & Detection)

Detection Steps:

• Monitor for unexpected changes to theme options via WordPress audit logs.
• Look for suspicious referrer headers in admin AJAX requests (e.g., requests originating from external domains).
• Use Web Application Firewall (WAF) rules to block requests to admin-ajax.php without a valid nonce.

Mitigation:

• Apply a virtual patch by adding nonce checks to the theme’s code (see Remediation section).
• Restrict admin access to trusted IPs.
• Educate administrators about phishing and CSRF risks.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-admin/admin-ajax.php with action=grandrestaurant_update_settings (or similar) from external referrers.
  • Unusual POST parameters containing script tags or unexpected values.
• Host IOCs:
  • Modified wp_options table entries for grandrestaurant_* options.
  • Presence of unexpected JavaScript in theme settings.
• Log IOCs:
  • WordPress debug log entries showing failed nonce checks (if patched).
  • Web server logs with POST /wp-admin/admin-ajax.php from non-admin IPs.

Detection Engineering

YARA Rule

rule Detect_GrandRestaurant_CSRF_Exploit {
    meta:
        description = "Detects CSRF exploit attempts against Grand Restaurant theme"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39351"
    strings:
        $ajax_action = "grandrestaurant_update_settings" nocase
        $admin_ajax = "admin-ajax.php" nocase
        $csrf_form = "<form" nocase
    condition:
        all of them
}

Sigma Rule

title: Grand Restaurant CSRF Exploit Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests targeting Grand Restaurant theme admin-ajax.php without proper referrer
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/admin-ajax.php'
        cs-referrer|contains: 'external-domain.com'
    condition: selection
falsepositives:
    - Legitimate cross-domain requests from trusted sources
level: medium

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2025-39351 Grand Restaurant CSRF Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=grandrestaurant_update_settings"; http_client_body;
    sid:1000001;
    rev:1;
    reference:cve,2025-39351;
    classtype:web-application-attack;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the theme until a patch is available, or switch to an alternative.
2. Add nonce verification to all AJAX handlers in the theme’s code. Example:

   if (!wp_verify_nonce($_REQUEST['_wpnonce'], 'grandrestaurant_nonce')) {
       wp_die('CSRF detected.');
   }
   

3. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php without a valid nonce parameter.

Long-Term Fix:

• Contact Themegoods for an official patch.
• Regularly update the theme to the latest version.
• Use a security plugin (e.g., Wordfence) that adds CSRF protection to admin actions.

Workaround:

• Restrict admin access to specific IP addresses.
• Require administrators to use a separate browser for admin tasks to reduce CSRF risk.

Valters IT
DevSecOps & Cyber Threat Intelligence