In early 2022, Microsoft shipped a critical security update for its Chromium-based Edge browser addressing a dangerous bug, tracked as CVE-2022-23261. This vulnerability caught the attention of security researchers and attackers alike due to its potential impact, which involved tampering with user data or altering browser integrity. In this post, I’ll break down what CVE-2022-23261 is, how it works, and show you a simplified snippet demonstrating the exploit, plus the crucial steps Microsoft took to close the hole.

What is CVE-2022-23261?

CVE-2022-23261 is a _tampering vulnerability_ affecting the Chromium-based version of Microsoft Edge. Tampering vulnerabilities allow an attacker to modify or manipulate data in a software system, potentially leading to security risks like unauthorized changes, theft, or code execution.

In this case, if a user visited a specially crafted website, an attacker could manipulate certain browser files or configuration, possibly elevating privileges or bypassing security restrictions.

References:

- NVD Entry for CVE-2022-23261
- Microsoft Security Guide

Why Does It Matter?

Edge is widely used in businesses and by general users due to its tight Windows integration. Tampering vulnerabilities are severe because attackers could abuse trusted software to change browser settings, steal data, install malicious extensions, or even redirect traffic without the user's knowledge.

The attacker uses the vulnerability to alter browser configuration or install rogue extensions.

3. These changes could persist, letting the attacker monitor web traffic, steal information, or deploy further malware.

Vulnerability Details

This bug lies in how Edge manages certain internal files and permissions. Due to improper handling of write permissions, a malicious site could _abuse JavaScript and browser APIs_ to trigger unintended file modifications on the user's device.

Microsoft’s advisory:
> “An elevation of privilege vulnerability exists in Microsoft Edge (Chromium-based) when the Edge browser improperly handles certain file operations. An attacker could exploit this vulnerability to inject or modify data.”
(Source)

How Was It Exploited?

Although Microsoft didn’t publish full exploit code, based on the description and similar Chromium issues, we can reconstruct a hypothetical attack. Imagine a scenario where a web page leverages service workers or the file system API to access and change key browser files it shouldn’t.

Here’s a simplified exploit code snippet

// Hypothetical: Trying to tamper with Edge's internal settings using FileSystem API

if ('chooseFileSystemEntries' in window) {
  // Ask user to pick a file (policy, config, extension settings)
  window.chooseFileSystemEntries().then(function(handle) {
    // Check if write access is possible - this should NOT be allowed for protected files!
    handle.createWritable().then(function(writer) {
      writer.write('Injected malicious config!');
      writer.close();
      alert('Browser settings have been tampered!');
    }).catch(function() {
      alert('Modification not allowed (patched).');
    });
  });
}

Security Note: In patched versions, protected files are off-limits, and the operation will fail with an access error.

Patch and Protection

Microsoft fixed CVE-2022-23261 by tightening file access permissions and restricting browser APIs from touching sensitive files/folders. Users simply need to update to the latest Edge version to be protected.

Official mitigation advice:

- Update Microsoft Edge immediately. (Latest downloads)

Responsible Disclosure and Timeline

- Discovery: Security researchers notice abnormal file access via Edge/Chromium APIs.

Final Thoughts

CVE-2022-23261 is a prime example of why routine browser updates are non-negotiable. Even a small flaw in how files are handled behind the scenes can expose users to real-world attacks.

Microsoft did not publicize any in-the-wild attacks before the patch, but the quick fix suggests the risk was real. Takeaways:

More Resources

- Microsoft Security Update
- Chromium Issue Tracker
- Edge Insider Changelog

Stay safe, and always patch your browser!

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*Originally written for tech readers wanting a clear, hands-on look at a real-world browser flaw.*

Timeline

Published on: 02/07/2022 17:15:00 UTC
Last modified on: 02/12/2022 01:27:00 UTC