In May 2024, security researchers discovered a DOM-based Cross-Site Scripting (XSS) vulnerability in Adobe Experience Manager (AEM), specifically in versions 6.5.20 and earlier. This serious vulnerability, identified as CVE-2024-36236, allows attackers to run arbitrary JavaScript on behalf of unsuspecting users — effectively hijacking their browser sessions. This post breaks down the vulnerability, how it works, and provides a sample exploitation scenario, all explained in straightforward American English.

What Is DOM-based XSS?

DOM-based XSS happens when a web application uses data from the Document Object Model (DOM) — often from the page URL — in JavaScript without proper sanitization. Malicious actors can craft special links that, when clicked, inject harmful code into the page. This type of attack takes place entirely within the client-side browser.

Attack Scenario

The vulnerability gets triggered when the application reflects data from the browser’s URL into the HTML page using JavaScript, *without* proper sanitization. If a user clicks a specially crafted link, the malicious script executes in their browser as if AEM itself had produced it, giving attackers a way to steal cookies, session tokens, or perform actions as the victim.

User interaction is required — for example, the victim must click a crafted link sent via email or posted on a forum.

Exploitation Details

Let’s look at a realistic example based on available advisories and typical AEM behaviors.

Some AEM pages might include code like this

<script>
  // Example of dangerous use of window.location
  var searchParam = window.location.hash.substr(1); // e.g., "q=<input>"
  document.getElementById('search').innerHTML = searchParam;
</script>


https://victim-aem-site.com/page#<img src="x" onerror="alert('XSS')">

When a victim clicks this link, the script assigns the contents of the URL fragment to the inner HTML of the page element, immediately triggering the attacker's code.

Here’s a minimal end-to-end example

<!-- Assume on AEM page: -->
<div id="search"></div>
<script>
  var param = window.location.hash.substr(1);
  document.getElementById('search').innerHTML = param;
</script>

Malicious URL

https://aem-victim.com/page#<img src=x onerror="alert(document.cookie)">

- Their browser runs the JavaScript from the hash (#) part — displaying an alert box with their cookies. An attacker could replace alert(document.cookie) with a script that silently sends those cookies to their server.

With successful exploitation, the attacker can

- Steal user cookies/session.

Potentially escalate attacks to deliver ransomware, phishing, or further malware.

This vulnerability is especially dangerous for admin users of AEM, who often have high privileges.

Adobe Security Advisory:

Adobe Security Bulletin APSB24-46

NVD Entry for CVE-2024-36236:

https://nvd.nist.gov/vuln/detail/CVE-2024-36236

About DOM-based XSS:

https://owasp.org/www-community/attacks/DOM_Based_XSS

Conclusion

CVE-2024-36236 makes clear how client-side scripting mistakes can create big security holes — even in major enterprise products like Adobe Experience Manager. The exploit needs a user to click a link, but that’s often easy for attackers to engineer via phishing. Updating AEM is the only sure fix. Be vigilant, stay patched, and review all code that uses user-supplied data in JavaScript.


Feel free to share this article, but remember: patch your AEM today — before attackers find you.

Timeline

Published on: 06/13/2024 08:16:22 UTC
Last modified on: 06/17/2024 20:21:20 UTC