In this post, we’ll explore CVE-2021-38728, a Cross-Site Scripting (XSS) vulnerability found in SEMCMS SHOP v1.1, specifically in the Ant_M_Coup.php file. Whether you're a student, developer, or a security professional, this guide will help you understand what happened, how attackers might exploit it, and what you can do to stay safe.

What is SEMCMS SHOP?

SEMCMS SHOP is a content management system (CMS) aimed at setting up shop or ecommerce websites. Its popularity makes it an interesting target for attackers, especially those looking for quick wins with XSS attacks.

Version: 1.1

- CVE ID: CVE-2021-38728

References:

- NVD Entry  
   - Exploit Database  

How Does the XSS Flaw Work?

The vulnerability exists because Ant_M_Coup.php handles user input improperly and fails to sanitize or encode certain parameters before returning them to the browser. Hackers can inject JavaScript code through a URL parameter, which will then be executed in the victim’s browser.

1. Understand the Attack Surface

The Ant_M_Coup.php file has a GET or POST parameter (for example, id, name, or another field) that is reflected back into an HTML page without being sanitized.

Suppose the vulnerable parameter is id. Here’s a simple evil payload

/admin/Ant_M_Coup.php?id=<script>alert('XSS')</script>

3. Send or Share the URL

An attacker can send this crafted link to an admin or user. When the victim clicks, their browser renders the page, executing the attacker’s JavaScript. This can be used for stealing session cookies, redirecting to phishing pages, or defacing the site.

Sample vulnerable PHP code

<?php
// Ant_M_Coup.php
$id = $_GET['id'];  // No sanitization
echo "<div>Coupon ID: $id</div>";  // Direct output
?>

Always sanitize output using htmlspecialchars()

<?php
$id = htmlspecialchars($_GET['id'], ENT_QUOTES, 'UTF-8');
echo "<div>Coupon ID: $id</div>";
?>

`

http://yourdomain.com/admin/Ant_M_Coup.php?id=alert('XSS')

Original References

- CVE Details at NVD
- Exploit Database Report
- Packet Storm Security Listing

Conclusion

CVE-2021-38728 shows how crucial it is to handle user input properly, even on seemingly minor admin pages. A single XSS bug like this can lead to total compromise of an e-commerce website. Always sanitize output, test for XSS, and apply vendor patches as soon as they’re available.

Stay safe, and happy coding!

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Timeline

Published on: 10/28/2022 16:15:00 UTC
Last modified on: 10/28/2022 18:46:00 UTC