CVE-2024-38700

Executive Summary

CVE-2024-38700 is a Code Injection vulnerability in the WordPress plugin WPCS (versions up to and including 1.2.0.3), developed by Realmag777. The flaw stems from improper neutralization of special elements in output used by a downstream component, allowing an unauthenticated attacker to inject arbitrary code. With a CVSS score of 6.5 (Medium), this vulnerability can lead to partial compromise of confidentiality, integrity, and availability. No public exploit or patch is currently available, but the risk is elevated due to the widespread use of WordPress plugins.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. WPCS is distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to verify the integrity of their plugin installations and monitor for unauthorized modifications. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors distributing tampered versions.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: Medium. The vulnerability is exploitable remotely without authentication, but the impact is limited to partial compromise. However, code injection can be chained with other vulnerabilities for greater effect.

Deep Dive & Mechanics

The vulnerability exists in the WPCS plugin, which is used for currency conversion and price display in WooCommerce. The plugin fails to properly sanitize output before passing it to a downstream component (likely JavaScript or PHP functions). An attacker can inject malicious code via crafted input parameters, such as currency symbols or price formats, which are then executed in the context of the WordPress site.

Root Cause: The plugin uses echo or print statements with user-supplied data without proper escaping or validation. For example, if the plugin outputs a currency symbol directly from a GET parameter, an attacker can inject JavaScript or PHP code.

Attack Vector: An unauthenticated attacker sends a specially crafted HTTP request to a vulnerable endpoint (e.g., /?currency=USD with injected code). The plugin processes this input and outputs it unsanitized, leading to code execution.

Impact: Successful exploitation allows the attacker to execute arbitrary code, potentially leading to site defacement, data theft, or further compromise of the WordPress installation.

Vulnerable vs. Patched Code

Vulnerable Code (WPCS <= 1.2.0.3):

// Example of vulnerable code in wpcs.php
function wpcs_display_currency($currency) {
    echo "<span class='wpcs-currency'>" . $currency . "</span>";
}
// The $currency variable is not sanitized

Patched Code (Hypothetical):

function wpcs_display_currency($currency) {
    $sanitized_currency = esc_html($currency);
    echo "<span class='wpcs-currency'>" . $sanitized_currency . "</span>";
}

Explanation: The patched version uses esc_html() to escape HTML entities, preventing code injection. Without this, an attacker can inject <script> tags or other malicious content.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with WPCS plugin version <= 1.2.0.3 installed and activated.
• Network access to the target.

Exploitation Steps:

1. Identify a vulnerable endpoint (e.g., /?currency=USD).
2. Craft a payload that injects JavaScript code:

   http://target.com/?currency=<script>alert('XSS')</script>
   

3. For code injection, use a PHP payload if the output is evaluated:

   http://target.com/?currency=;system('id');
   

4. Observe the injected code execution in the browser or server response.

Proof of Concept (PoC):

curl "http://target.com/?currency=<script>alert('CVE-2024-38700')</script>"

Blue Team (Detection & Defense)

Detection:

• Monitor web server logs for suspicious query parameters containing <script>, <?php, or other code patterns.
• Use WAF rules to block requests with special characters in currency parameters.

Defense:

• Disable or remove the WPCS plugin until a patch is available.
• Implement input validation and output encoding for all user-supplied data.
• Use a Web Application Firewall (WAF) to filter malicious payloads.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests with query parameters containing <script>, <?php, or system(.
  • Unusual POST requests to WPCS endpoints with encoded payloads.
• File IOCs:
  • Modified wpcs.php or other plugin files with injected code.
  • New files in wp-content/uploads/ or wp-content/plugins/wpcs/ with suspicious content.
• Log IOCs:
  • Web server logs showing 404 errors for non-existent endpoints with injected parameters.
  • PHP error logs indicating eval() or assert() calls.

Detection Engineering

YARA Rule

rule CVE_2024_38700_WPCS_Code_Injection {
    meta:
        description = "Detects code injection attempts targeting WPCS plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-38700"
    strings:
        $payload1 = /<script[^>]*>.*<\/script>/i
        $payload2 = /<?php/i
        $payload3 = /system\(/i
        $payload4 = /eval\(/i
    condition:
        any of ($payload*) and filesize < 10KB
}

Sigma Rule

title: CVE-2024-38700 WPCS Code Injection Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests with code injection patterns targeting WPCS plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - '<script'
            - '<?php'
            - 'system('
            - 'eval('
    condition: selection
falsepositives:
    - Legitimate use of special characters in currency names (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-38700 WPCS Code Injection Attempt"; flow:to_server,established; content:"GET"; http_method; content:"/?"; http_uri; pcre:"/(<script|<?php|system\(|eval\()/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the WPCS plugin until a patch is released.
2. Implement a Web Application Firewall (WAF) rule to block requests containing <script>, <?php, or system( in query parameters.
3. Monitor logs for exploitation attempts and respond accordingly.

Long-Term Fix:

• The vendor (Realmag777) must release a patched version that properly sanitizes output using esc_html(), esc_attr(), or similar WordPress functions.
• Users should update to the latest version once available.
• Consider replacing WPCS with an alternative plugin that is actively maintained.

Workaround:

• Add the following code to the theme's functions.php to sanitize the currency parameter:

add_filter('query_vars', function($vars) {
    $vars[] = 'currency';
    return $vars;
});
add_action('wp', function() {
    if (get_query_var('currency')) {
        set_query_var('currency', esc_html(get_query_var('currency')));
    }
});

Valters IT
Securing Digital Frontiers