In the fast-moving world of browsers, Microsoft Edge—now running on Chromium—has become a go-to for Windows users. But like all software, it isn’t perfect. One notable flaw made headlines in 2023: CVE-2023-36409, an information disclosure vulnerability. Here, I break down what it is, how it works, plus a simple explanation and code snipplet to give you the inside scoop on this bug.

What is CVE-2023-36409?

CVE-2023-36409 is a vulnerability found in Microsoft Edge (Chromium-based) that lets an attacker steal information they shouldn’t have access to. This bug was patched in Edge version 114..1823.51, but for anyone using an older version, it posed a real risk.

- Microsoft Security Guide - CVE-2023-36409
- Chromium Releases Blog - Edge Security Updates

How Does The Vulnerability Happen?

This bug is an example of an **information disclosure* flaw in a web browser’s component. Chromium’s sandbox is meant to keep websites isolated, so malicious code on one site can't grab stuff from another. But with this bug, attackers could use certain JavaScript tricks to leak memory or sensitive browser data.

Microsoft’s official advisory is vague, but security researchers say the bug likely comes from how Chromium-based Edge handled certain JavaScript API calls—possibly window interaction or cross-origin communication that should’ve been blocked.

Simple Example: How an Attacker Could Exploit CVE-2023-36409

Let’s say there’s a webpage using a crafty script. The attacker tricks a user into visiting their site. Through a browser bug, the script pulls information from another website or even private files loaded in other tabs!

Imagine this in JavaScript pseudocode

// * Hypothetical Exploit Snippet *
// Tries to bypass Same-Origin Policy and read data from another tab/window

let secretWindow = window.open("https://sensitive-site.com";, "targetWindow");
setTimeout(() => {
    try {
        // Normally blocked by browsers!
        let leakedData = secretWindow.document.body.innerText;
        console.log("Leaked info:", leakedData);
    } catch (err) {
        console.error("Access denied (as expected)", err);
    }
}, 200);

In a safe browser, this code throws an error (blocked by the Same-Origin Policy). But with CVE-2023-36409, the attacker’s code might get access to restricted data—like text inside a user’s email or banking site.

*Note: The actual exploit code is more complex, working at a lower level with browser internals but the idea is the same—breaking browser isolation to steal information.*

Affected Versions: Edge before 114..1823.51

In technical terms, the bug involved the "Site Isolation" feature not fully protecting against specific JavaScript interaction types. This allowed clever scripts to sidestep security checks.

Why Is This Fix Important?

If left unpatched, any site could try to steal your session info, private messages, or important data simply by you visiting a tainted web page. That’s why keeping browsers up to date is so important—vulnerabilities like this are goldmines for hackers.

How to Stay Safe

1. Update Edge: Always keep your browser updated. Edge now updates automatically, but click the three dots > Help and feedback > About Microsoft Edge to check.

3. Use Security Extensions: Security or privacy extensions may help, but nothing replaces a secure browser itself.

More to Read

- Microsoft Security Guide - CVE-2023-36409
- Edge Release Notes
- Research on Chromium Site Isolation

Conclusion

CVE-2023-36409 is a textbook example of how browser bugs can put your private info at risk. While this specific hole has been patched, always update your browsers and keep security top of mind. You never know what’s lurking in your favorite apps until researchers find and report it.

Timeline

Published on: 11/07/2023 00:15:07 UTC
Last modified on: 11/14/2023 18:51:23 UTC