A newly discovered vulnerability, dubbed CVE-2023-4051, has surfaced which allows an attacker to potentially obscure the full-screen notification by using the file open dialog. This could lead to user confusion and possible spoofing attacks, posing a significant threat to user security and privacy. This vulnerability affects Firefox < 116, Firefox ESR < 115.2, and Thunderbird < 115.2. In this post, we'll dive deep into the exploit details, provide a code snippet to demonstrate the issue, and share valuable resources to help you stay protected.

1. Official CVE entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4051
2. Mozilla Foundation Security Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2023-11/
3. NVD (National Vulnerability Database) entry: https://nvd.nist.gov/vuln/detail/CVE-2023-4051

Exploit Details

To better understand how this vulnerability works, let's take a closer look at the issue. The exploit takes advantage of the file open dialog to obscure the full-screen notification, which is a security feature implemented to alert users when a website enters full-screen mode. The attacker uses JavaScript to create a unique combination of events that trigger the file open dialog while the website is in full-screen mode, allowing the attacker to potentially spoof a legitimate website and trick the user into providing sensitive data or downloading malicious software.

Here's a simple code snippet to demonstrate the exploit

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.">
    <title>Obscuring Full Screen Notification - CVE-2023-4051</title>
    <button id="fullscreenBtn">Go Fullscreen</button>
    <input type="file" id="fileInput" style="display:none;">
        const fullscreenBtn = document.getElementById("fullscreenBtn");
        const fileInput = document.getElementById("fileInput");

        fullscreenBtn.addEventListener("click", () => {
            setTimeout(() => {
            }, 1);

In this example, when the user clicks the "Go Fullscreen" button, the website enters full-screen mode. Immediately after, the hidden file input is clicked programmatically, triggering the file open dialog and obscuring the full-screen notification.

Remediation Steps

To mitigate this vulnerability and protect your system from potential spoofing attacks, or data leaks resulting from CVE-2023-4051, it's recommended to update the affected software to the latest version as soon as possible. Follow these steps:

1. Update Firefox to version 116 or later: https://www.mozilla.org/en-US/firefox/new/
2. Update Firefox ESR to version 115.2 or later: https://www.mozilla.org/en-US/firefox/organizations/
3. Update Thunderbird to version 115.2 or later: https://www.thunderbird.net/en-US/


CVE-2023-4051 is a potentially serious security vulnerability that could lead to user confusion and spoofing attacks when exploited. It's crucial to keep yourself informed, understand how this exploit works, and update your software to the latest versions to protect yourself from potential threats. Stay vigilant, and stay safe!


Published on: 08/01/2023 15:15:00 UTC
Last modified on: 09/11/2023 09:15:00 UTC