A recently discovered vulnerability, identified as CVE-2024-1549, has been found to affect Firefox, Firefox ESR, and Thunderbird versions earlier than 123, 115.8, and 115.8, respectively. This vulnerability is due to the implementation of custom cursors, which can lead to portions of the cursor overlapping the permission dialog. Consequently, this may cause user confusion and lead to undesired permission grants.

In this article, we will provide an in-depth explanation of this security flaw, including a sample code snippet that demonstrates the vulnerability, references to original sources, and details about the potential exploit.

The Vulnerability

The CVE-2024-1549 vulnerability arises from the way browsers, such as Firefox and Thunderbird, handle custom cursors. When a website sets an unusually large custom cursor, portions of the cursor may overlap with the permission dialog displayed to the user, resulting in potential user confusion and unexpected permission grants.

To help illustrate the vulnerability, consider the following sample code snippet

<!DOCTYPE html>
<html>
<head>
<style>
.custom-cursor {
    cursor: url('large-cursor.png') 128 128, auto;
}
</style>
</head>
<body>
<div class="custom-cursor">
    Hover over me to see the custom cursor!
</div>
<script>
document.querySelector(".custom-cursor").addEventListener("mouseenter", function() {
    navigator.geolocation.getCurrentPosition(function(position) {
        console.log("Granted geolocation permission.");
    });
});
</script>
</body>
</html>

In this example, a large custom cursor is applied to a specific element within the web page. When the user hovers over this element with their cursor, the website will request permission to access the user's geolocation. If the custom cursor unexpectedly overlaps the permission dialog, the user may accidentally grant permission without fully understanding the implications.

This vulnerability was initially reported by the Mozilla Security Team and can be found in the following security advisories:

1. Mozilla Foundation Security Advisory 2024-14
2. Mozilla Foundation Security Advisory 2024-15
3. Mozilla Foundation Security Advisory 2024-16

These advisories provide detailed information about the CVE-2024-1549 vulnerability and its effects on various Mozilla products.

Exploit Details

Exploiting this vulnerability requires an attacker to create a malicious website that employs a large custom cursor, which can potentially lead to the aforementioned permission dialog overlapping. Once successful, the attacker can confuse the user and trick them into granting unwanted permissions, such as access to their geolocation, microphone, or camera.

It is important to note that this security issue is characterized by its potential to cause user confusion and is largely dependent on users not being aware of the malicious intent.

How to Protect Yourself

To address this vulnerability, update your Mozilla browser or email client to the latest versions as follows:

Thunderbird: Update to version 115.8 or later

By doing so, you can ensure that your browser and email client are no longer susceptible to the CVE-2024-1549 vulnerability, guarding you against potential permission dialog overlapping and associated attacks.

Conclusion

The CVE-2024-1549 vulnerability presents a significant security risk to users of Mozilla products, specifically Firefox, Firefox ESR, and Thunderbird. By understanding the nature of this vulnerability and taking appropriate action—namely, updating your software to the latest version—you can protect yourself from potential attacks. As always, it is crucial to remain vigilant and attentive when navigating the web and granting permissions to websites.

Timeline

Published on: 02/20/2024 14:15:08 UTC
Last modified on: 03/04/2024 09:15:37 UTC