CVE-2025-23676

Executive Summary

CVE-2025-23676 is a reflected Cross-Site Scripting (XSS) vulnerability in the LH Email WordPress plugin (slug: lh-email) by shawfactor, affecting versions up to and including 1.12. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into a reflected response. This can lead to session hijacking, credential theft, or defacement within the context of the victim’s browser session on the WordPress site.

As this is a WordPress plugin vulnerability, the attack surface is limited to sites running the vulnerable plugin. No public exploit code or proof-of-concept is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. However, the lack of a patch from the vendor increases risk for unmaintained 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 admin dashboard or directly from the repository are affected. No third-party package manager (NPM, PyPI, Go, Ruby) is involved. The plugin is not available on any other package registry.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – victim must click a crafted link
• Scope: Changed (S:C) – injected script can affect resources beyond the vulnerable component
• Confidentiality Impact: Low (C:L) – limited data exposure
• Integrity Impact: Low (I:L) – limited modification of content
• Availability Impact: Low (A:L) – limited disruption

Threat Level: High. While exploitation requires user interaction, the lack of a patch and the widespread use of WordPress make this a significant risk for unmaintained sites.

Deep Dive & Mechanics

The vulnerability exists in the lh-email plugin, which provides email-related functionality for WordPress. The plugin fails to properly sanitize or escape user-supplied input before reflecting it in the HTTP response. Specifically, a parameter (likely email or similar) is echoed back without proper encoding, allowing an attacker to inject arbitrary HTML and JavaScript.

Attack Flow:

1. Attacker crafts a malicious URL containing a JavaScript payload in a vulnerable parameter.
2. Victim (authenticated or unauthenticated) clicks the link.
3. The WordPress server processes the request and reflects the payload in the response without sanitization.
4. The victim’s browser executes the injected script, which can steal cookies, redirect to phishing pages, or perform actions on behalf of the victim.

Root Cause: The plugin uses functions like echo $_GET['param'] or similar without applying WordPress’s esc_html(), esc_attr(), or wp_kses() functions.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical fix based on standard WordPress security practices.

Vulnerable Code (lh-email <= 1.12):

<?php
// Example vulnerable code
$email = $_GET['email'];
echo "You entered: " . $email;
?>

Patched Code (Hypothetical):

<?php
// Properly escape output
$email = isset($_GET['email']) ? sanitize_email($_GET['email']) : '';
echo "You entered: " . esc_html($email);
?>

The patched version uses sanitize_email() to validate the input and esc_html() to encode output, preventing script injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with LH Email plugin version <= 1.12 installed and active.
• No authentication required for the vulnerable endpoint.

Exploit Payload:

http://target.com/wp-content/plugins/lh-email/some-file.php?email=<script>alert('XSS')</script>

Steps:

1. Identify the vulnerable parameter (e.g., email, subject, or message) by fuzzing the plugin’s endpoints.
2. Craft a URL with a JavaScript payload:

   http://target.com/wp-content/plugins/lh-email/process.php?email=<img src=x onerror=alert(document.cookie)>
   

3. Deliver the link to the victim via email, social engineering, or other means.
4. When the victim clicks the link, the script executes in their browser.

Note: No public exploit code is available; this is a conceptual example.

Blue Team (Defense & Detection)

Detection:

• Monitor web server logs for requests containing <script, onerror, onload, or other XSS indicators in query parameters.
• Use a Web Application Firewall (WAF) to block reflected XSS patterns.

Mitigation:

• Disable or remove the LH Email plugin immediately if no patch is available.
• Implement Content Security Policy (CSP) headers to restrict script execution.
• Use WordPress security plugins (e.g., Wordfence) to add virtual patching.

Indicators of Compromise (IOCs)

• URL Patterns:
  • */wp-content/plugins/lh-email/*?email=*<script*
  • */wp-content/plugins/lh-email/*?email=*<img*onerror*
• HTTP Request Parameters:
  • email containing HTML tags or JavaScript code.
• Log Entries:
  • GET /wp-content/plugins/lh-email/process.php?email=<script>alert(1)</script> HTTP/1.1
• File Hashes (Plugin Files):
  • No specific hashes available; monitor for unexpected modifications to plugin files.

Detection Engineering

YARA Rule

rule CVE_2025_23676_LH_Email_XSS {
    meta:
        description = "Detects reflected XSS attempts targeting LH Email plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-23676"
    strings:
        $xss1 = /email=.*<script/i
        $xss2 = /email=.*<img.*onerror/i
        $xss3 = /email=.*onload/i
        $xss4 = /email=.*javascript:/i
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt Against LH Email Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects reflected XSS attempts targeting the LH Email WordPress plugin (CVE-2025-23676)
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'email=<script'
            - 'email=<img'
            - 'email=javascript:'
    condition: selection
falsepositives:
    - Legitimate use of email parameter with special characters (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (msg:"CVE-2025-23676 LH Email Reflected XSS Attempt"; flow:to_server,established; content:"/wp-content/plugins/lh-email/"; http_uri; pcre:"/email=.*(<script|<img.*onerror|javascript:)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete the LH Email plugin from all WordPress installations.
2. Virtual Patching: Use a WAF to block requests containing XSS patterns in the email parameter.
3. Monitor Logs: Review web server logs for exploitation attempts.

Long-Term Fix:

• Since no patch is available, consider migrating to an alternative email plugin that is actively maintained.
• If the plugin is critical, manually apply the fix by escaping output in the plugin’s PHP files (see Vulnerable vs. Patched Code section).

General Best Practices:

• Keep all WordPress plugins and themes updated.
• Implement a Content Security Policy (CSP) to mitigate XSS impact.
• Use WordPress security plugins with virtual patching capabilities.

Valters IT