Plugin Name	Funnel Builder by FunnelKit
Type of Vulnerability	Cross-Site Scripting (XSS)
CVE Number	CVE-2025-66067
Urgency	Low
CVE Publish Date	2025-12-08
Source URL	CVE-2025-66067

WordPress Funnel Builder (FunnelKit) XSS Vulnerability (CVE-2025-66067): Immediate Steps for Site Owners — Managed-WP Security Advisory

Author: Managed-WP Security Team

Summary: A Cross-Site Scripting (XSS) vulnerability has been identified in the Funnel Builder by FunnelKit plugin (versions up to 3.13.1.2), tracked as CVE-2025-66067. This advisory breaks down the technical context, attack scenarios, practical detection and mitigation, plus how Managed-WP can shield your WordPress site instantly—even before applying the official update (3.13.1.3).

Table of Contents

• Incident Summary and Impact
• Technical Analysis and Vulnerability Scope
• Potential Attack Vectors and Exploitability
• Real-World Threat Scenarios and Consequences
• Detection Measures for Immediate Action
• Short-Term Security Controls (Rapid Mitigation)
• Long-Term Remediation and Security Best Practices
• How Managed-WP Protects You
• Incident Response Protocol
• Recommended WAF Rules and Scanning Tools
• Security Policies and Hardening Guidelines
• Getting Started with Managed-WP Protection
• FAQs
• Appendix: Useful Commands and Queries

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Incident Summary and Impact

On December 6, 2025, a stored Cross-Site Scripting (XSS) flaw was officially disclosed for the Funnel Builder by FunnelKit WordPress plugin. The vulnerability affects all versions up to and including 3.13.1.2, with a patch provided in 3.13.1.3.

This vulnerability allows an attacker with Contributor level access or higher to inject malicious HTML or JavaScript code into the plugin’s content areas, which is then stored and rendered in the WordPress admin interface or on front-end pages.

Although rated with medium severity (CVSS score 6.5), this flaw represents a significant risk: from admin session takeovers and privilege escalations to persistent threats against site visitors.

Managed-WP strongly advises all site owners and administrators to take this vulnerability seriously and act swiftly to prevent exploitation.

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Technical Analysis and Vulnerability Scope

• Affected Plugin: Funnel Builder by FunnelKit
• Affected Versions: Versions <= 3.13.1.2
• Fixed Version: 3.13.1.3
• Type: Stored Cross-Site Scripting (XSS)
• Required Privilege: Contributor (or higher)
• CVE Identifier: CVE-2025-66067
• OWASP Category: A3 – Injection

Root Cause: Insufficient escaping and sanitization of user-supplied input stored in the database, which is output as active HTML/JS in funnels, forms, or builder widgets accessible in both admin and front-end contexts.

Note: Contributors typically cannot publish directly, but if your site allows file uploads or dynamic shortcode/widget usage by Contributors, the risk of attacker payloads executing for administrators or visitors increases considerably.

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Potential Attack Vectors and Exploitability

• Privileges Needed: Contributor role or above
• Risk Factors:
  • Open user registration assigning Contributors automatically increases exposure.
  • Credential theft or reuse may enable attackers to gain Contributor access.
  • Editor or Author account compromises can facilitate lateral movement.
• Attack Complexity: Low to moderate – crafting payloads is straightforward; obtaining account access is the main barrier.
• Likelihood: Moderate on sites with open registration or weak user vetting policies.

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Real-World Threat Scenarios and Consequences

1. Admin Targeted Stored XSS:
   • Malicious script embedded in funnel or form content.
   • Executes in admin browsers when reviewing content, leading to cookie theft or session hijacking.
   • Potential outcomes: full admin takeover, installation of backdoors, or privilege escalation.
2. Persistent Customer-Facing XSS:
   • Injected scripts run in site visitors’ browsers.
   • Risk: phishing attacks, malicious redirects, or harmful payload delivery.
   • Impact: reputational damage, SEO penalties, data compromise.
3. Supply Chain & Pivoting:
   • Using XSS payloads to load external malicious scripts or iFrames.
   • Enables attackers to establish footholds for subsequent attacks.
4. Phishing and Social Engineering:
   • Deceptive UI elements or fake login prompts to capture admin credentials.

Even though exploitation requires Contributor access, these scenarios are very feasible on sites with multiple authors or insufficient registration controls.

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Detection Measures for Immediate Action

Site owners should quickly verify:

• Installed plugin version — confirm it is higher than 3.13.1.2.
• Review recent content from Contributor users for suspicious code snippets, including:
  • <script> tags or event handlers (e.g. onerror=, onclick=).
  • javascript:, data:, or base64-encoded strings embedded in fields.
  • iframe tags pointing to external domains.
  • Obfuscated code using eval(), atob(), or other decoding functions.
• Audit admin dashboard pages where such content is rendered, using isolated or sandboxed browsers.
• Examine logs for abnormal admin actions, new users, or plugin installs.
• Check server outbound connections for unknown or suspicious destinations.
• Monitor critical files for unauthorized changes (themes, uploads, options).

Sample database queries to find suspicious content:

• Posts containing scripts:

  SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%<script%';

• Options storing scripts:

  SELECT option_name FROM wp_options WHERE option_value LIKE '%<script%';

• Search uploads directory:

  grep -R --line-number "<script" wp-content/uploads

Note: Many page builders include HTML snippets; focus on scripts and suspicious encoded payloads.

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Short-Term Security Controls (Rapid Mitigation)

If updating immediately is not an option, implement these mitigations to limit exposure:

1. Deploy Managed-WP WAF rules:
   • Block requests containing known exploit payloads targeting Funnel Builder endpoints.
2. Restrict user registration and roles:
   • Disable public registrations or set new users to Subscriber role.
3. Implement or tighten Content Security Policy (CSP):
   • Disallow inline and external scripts except from trusted sources.
   • Example: Content-Security-Policy: default-src 'self'; script-src 'self';
4. Harden Admin Access:
   • Enforce two-factor authentication for all privileged accounts.
   • Restrict WP-Admin access by IP or HTTP authentication where feasible.
5. Sanitize custom user input:
   • Use WordPress escaping functions like esc_html(), esc_attr(), and wp_kses_post() in custom code.
6. Scan for and clean injected content:
   • Use Managed-WP’s scanner or reputable malware tools to detect and remove malicious scripts.
7. Reduce Contributor capabilities temporarily:
   • Remove unnecessary meta boxes or file upload rights.
8. Enable plugin auto-updates:
   • Schedule an immediate update once the patched version is released.

These measures help minimize risk and provide a window to safely upgrade.

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Long-Term Remediation and Security Best Practices

1. Update to Funnel Builder version 3.13.1.3 or newer:
   • Test updates on staging sites to ensure compatibility.
2. Review and enforce user roles and registration policies:
   • Restrict Contributor and higher roles from automatic assignment.
   • Implement registration approval workflows if needed.
3. Improve coding and templating standards:
   • Always escape and sanitize output (esc_html, esc_attr, wp_kses).
   • Sanitize inputs on save with functions like sanitize_text_field() or wp_kses_post().
4. Harden Server and WordPress security posture:
   • Maintain up-to-date PHP and webserver versions.
   • Apply secure file permissions and disable PHP execution in uploads if possible.
   • Protect critical files (wp-config.php) and use strong database credentials.
5. Use continuous scanning and virtual patching:
   • Implement a WAF with virtual patching capabilities to block exploit attempts during patch rollout.
   • Regularly scan plugin and theme files for unauthorized modifications.
6. Monitoring and Logging Enhancements:
   • Track key user actions, especially around plugins and content.
   • Alert on new plugin activations or admin email changes.

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How Managed-WP Protects You

Managed-WP deploys a robust, layered strategy to neutralize threats like CVE-2025-66067:

• Expertly managed WAF rules: Precisely tuned rules to detect and block XSS exploit attempts, especially targeting Funnel Builder.
• Virtual patching: Real-time traffic filtering that protects sites even before official patches are applied—no plugin code changes required.
• Comprehensive malware scanning and cleanup: Detects injected scripts across posts, meta, uploads, and plugin/theme files, with hands-on remediation options.
• Role hardening and access controls: Recommendations and assistance to restrict Contributor capabilities and tighten admin security.
• Automated updates and alerts: Notifications for vulnerable plugins and the ability to safely auto-update trusted plugins.
• Incident response support: Guided containment, forensics, and post-incident hardening if exploitation is suspected or detected.

Our layered defense approach buys critical time and reduces risk in complex environments where immediate patching isn’t always feasible.

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Incident Response Protocol

If you suspect your site has been compromised, follow these steps immediately:

1. Containment:
   • Disable public content creation mechanisms (close registrations).
   • Put your site into maintenance mode to prevent further exploitation.
   • Isolate the instance for forensic evidence collection (filesystem snapshots, database dumps).
2. Evidence Preservation:
   • Export server and plugin logs.
   • Save suspicious content offline – do not load in a production environment.
3. Identification:
   • Trace malicious content insertion to specific users and times.
   • Run searches on wp_posts, wp_postmeta, and wp_options for script-based injections.
   • Review recently altered files or plugins/themes.
4. Removal and Remediation:
   • Clean injected scripts manually or with vetted tools.
   • Reinstall and update Funnel Builder plugin from trusted sources.
   • Replace altered core or theme files with clean copies.
5. Credential and Access Control:
   • Force password resets for all users with admin or editor roles.
   • Invalidate existing sessions by updating salts in wp-config.php.
   • Audit and remove any suspicious user accounts.
6. Patch and Harden:
   • Complete plugin updates immediately.
   • Enforce 2-factor authentication and IP restrictions for admin areas.
7. Post-Mortem and Monitoring:
   • Document incident timeline and corrective actions.
   • Implement continuous monitoring and WAF rules to prevent recurrence.

Managed-WP’s incident response team is available to assist with detailed containment and cleanup actions.

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Recommended WAF Rules and Scanning Tools

Below are sample intrusion prevention rules you can use in your WAF (ModSecurity, NGINX, or custom Managed-WP rules). Test thoroughly on staging before deployment.

ModSecurity Example Rule:

# Block script tags or javascript: in POST bodies targeting Funnel Builder endpoints
SecRule REQUEST_URI "@pm /wp-admin/admin.php /wp-json/funnelkit /funnel-builder" "phase:2,chain,deny,log,msg:'Block XSS payloads targeting FunnelBuilder',id:1001001"
  SecRule ARGS_NAMES|ARGS|REQUEST_BODY "@rx (<script|javascript:|onerror=|onload=|eval\(|atob\(|unescape\()" "t:none,t:urlDecode,t:lowercase"

NGINX (ngx_lua) Example:

location /wp-admin/ {
  access_by_lua_block {
    ngx.req.read_body()
    local body = ngx.req.get_body_data()
    if body and body:lower():find("<script") then
      ngx.log(ngx.ERR, "Blocked request containing <script>")
      return ngx.exit(403)
    end
  }
  proxy_pass http://backend;
}

WP-CLI SQL Query to Detect Suspicious Content:

wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%<script%';"

Regex for encoded JS detection (use with caution):

• /(?:(?:<script\b[^>]*>.*?</script>)|(?:javascript:)|(?:onerror\s*=))/is

Important: Fine-tune rules to avoid false positives, as many builders use legitimate HTML snippets that may trigger naïve patterns.

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Security Policies and Hardening Guidelines

• Avoid granting file upload permissions to Contributors or Authors unless necessary.
• Label and treat users capable of inserting HTML fragments as higher risk; implement stricter review workflows.
• Maintain an updated inventory of plugins and monitor for vulnerabilities monthly.
• Use staging environments to test plugin updates before deploying to production.
• Keep reliable backups and test restore procedures regularly.
• Restrict unnecessary XML-RPC and REST API access.
• Sanitize all user-submitted HTML server-side using wp_kses() with a strict allowed tags whitelist.

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Getting Started with Managed-WP Protection

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• Professional, managed firewall rules tailored for WordPress
• Unlimited bandwidth and real-time WAF to block exploit attempts
• Malware scanning across posts, metadata, and uploads
• Mitigation of critical OWASP Top 10 risks, including XSS
• Quick onboarding with no code changes required

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For automatic cleanup, virtual patching, and priority support, our paid plans deliver expert hands-on services that eliminate risk efficiently. But the free plan is an excellent starting point for meaningful protection right away.

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FAQs

Q: If my site has no Contributors, am I safe?

A: While the risk is reduced, attackers often compromise higher role accounts via credential theft or phishing. Review all plugins and themes for similar issues.

Q: Can WAF protection replace plugin updates?

A: No. WAFs reduce exposure and buy time but are not a permanent substitute for applying official patches. Always update promptly.

Q: Is Content Security Policy (CSP) effective?

A: CSP adds a valuable layer but must be applied carefully, especially with complex builders. Consider report-only mode to tune your policy.

Q: How do I safely remove injected scripts?

A: Manual cleanup by a skilled admin or security vendor is safest. Automated tools may risk unintended damage—ensure backups exist.

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Appendix: Useful Commands and Detection Queries

• Check plugin details:
  wp plugin get funnel-builder --fields=name,version,status
• Search posts with suspicious tags:
  wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content REGEXP '<(script|iframe|object|embed)';"
• Look for meta values with scripts:
  wp db query "SELECT meta_id, post_id, meta_key FROM wp_postmeta WHERE meta_value REGEXP '<(script|iframe|javascript:)';"
• Scan uploads for malicious content:
  grep -R --line-number -E "<script|javascript:|onerror=" wp-content/uploads || true
• Find recently modified files:
  find . -type f -mtime -30 -print

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Final Recommendations

The CVE-2025-66067 vulnerability exemplifies the ongoing need for diligent security in WordPress site management—especially for features accepting user-generated HTML. Site owners must:

• Promptly update the Funnel Builder plugin to version 3.13.1.3 or newer.
• Apply immediate mitigations, including disabling risky user registrations and enabling a WAF.
• Harden admin access and implement continuous monitoring to catch suspicious activities early.

Managed-WP is here to support you through rapid virtual patching, malware cleanup, and ongoing protection. Whether you start with our free plan or select a managed subscription, the key is decisive, proactive action.

Stay vigilant, act fast, and if needed, contact our security team for expert guidance through every phase of incident response.

— Managed-WP Security Team

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