CVE-2024-8907 is a medium-severity security bug that was found in Google Chrome for Android. The issue lies in the Omnibox—the address bar at the top of Chrome—which did not validate user input correctly before version 129..6668.58. This allowed a remote attacker, who convinced a victim to perform specific user interface gestures, to inject and execute malicious JavaScript or HTML on the device. This type of vulnerability is called Cross-Site Scripting (XSS).

Recommendations and fixes

All information here is simplified for better clarity and uniquely presented.

Understanding the Omnibox Flaw

Chrome’s Omnibox is meant to show website addresses and sometimes suggest queries, but should never run code or allow anyone to tamper with its content display, especially not in a way that could let a hacker control what the browser executes.

The bug was due to insufficient input validation—Chrome didn’t carefully check special inputs passed to it. If a user was convinced to perform a certain sequence of gestures (like drag-and-drop or copying and pasting a link), a hacker could inject code into the Omnibox, which then got executed when shown.

Why This is Dangerous

XSS attacks can let a hacker steal cookies, impersonate users, show fake login forms, or redirect users to malicious websites. On mobile, this risk is amplified by users’ tendency to trust browser UI.

Exploit Walk-through

Please note: The following is for educational purposes only! Never attack servers or devices you do not own or have permission to test.

Step 1: Crafting Malicious Data

Suppose an attacker builds the following piece of HTML/JavaScript, hosted on their server (say, hacker.com):

<!-- Malicious Page: xss_test.html -->
<a href="javascript:alert('XSS Vulnerability!')" id="dangerLink">Tap and Hold Here</a>
<script>
document.getElementById('dangerLink').addEventListener('click', function(e) { 
    // Fakes drag-and-drop/copy input to trick user and the Omnibox
    window.prompt('Copy this link and open a new tab to paste it in Omnibox!');
});
</script>

The attacker asks the victim to long-press (tap-and-hold) the link, copy it (as prompted by their browser’s context menu), then manually paste it into the Omnibox and press enter.

Step 2: What Happens in Chrome (Before Patch 129..6668.58)?

In Chrome versions before 129..6668.58, pasting this crafted string in the Omnibox might not be properly sanitized. If Chrome mistakenly treats the javascript: pseudo-URL as active code, it runs the alert, which could instead be a more dangerous payload.

Example JavaScript/HTML Payload

javascript:alert(document.cookie); // Could be more malicious (stealing data, etc.)

User follows the instructions: long-presses, copies, pastes into Omnibox, and loads the page.

3. Chrome (pre-patch) might run the code, showing the alert or worse – executing attacker-chosen scripts.

Visual Diagram

[User] -> Visits attacker site -> UI Gesture (Copy link) -> Paste in Omnibox -> XSS Executes

Why the Gesture Is Needed

This attack vector needs specific UI participation (copy+paste via the address bar), so it’s not a “drive-by” attack. But, clever social engineering (think: "Copy this link for a prize!") could get people to do it.

Fixed Version and Patches

Google fixed the bug in:

Chrome for Android 129..6668.58

Patch details:
- Chromium Release Notes
- Chromium Bug Tracker (restricted, summary only)

The patch ensures that anything pasted into the Omnibox—even after complex gestures—gets properly sanitized and treated as text, not code, closing the door for script injection.

How input should be sanitized (pseudo-code)

def sanitize_input(user_input):
    if user_input.startswith('javascript:'):
        # Strip or ignore dangerous schemes
        return ''
    # further sanitation...
    return user_input

Or in JavaScript/Chromium C++ context, never allow the Omnibox to execute code directly from user input under any sequence of gestures.

References

- Chromium Security Advisory
- CVE-2024-8907 Details on NVD
- Omnibox Security Improvements

Conclusion

CVE-2024-8907 is a classic reminder that even highly polished browsers like Chrome can be susceptible to edge case input handling bugs, especially when UI gestures are involved. Always keep your browsers up to date and follow safe browsing habits.

Timeline

Published on: 09/17/2024 21:15:13 UTC
Last modified on: 09/23/2024 18:23:57 UTC