CVE-2023-4077 points to a security flaw in Google Chrome's Extensions platform, patched before version 115..579.170. In simple terms, attackers could abuse insufficient data checks in Chrome extensions and potentially inject malicious scripts or HTML into the browser’s privileged pages. This medium-severity vulnerability highlights the dangers of trusting browser extensions and how a bit of unvalidated data can open doors for cyber attackers.

In this long-read, we’ll break down what happened, look at a code snippet showing the pitfall, explore possible exploits, and provide links to original references.

What is CVE-2023-4077?

In Chrome, browser extensions can run with powerful permissions, sometimes interacting with parts of the browser ordinary web pages can’t touch—these are the so-called “privileged pages.” While Chrome tries to make sure only safe data passes between extensions and the browser, older Chrome builds missed some crucial validation checks.

> If a user was tricked into installing a malicious extension, the attacker could inject scripts (potential for XSS or privilege escalation) or HTML into these privileged environments.

Malicious Extension Submission

The attacker uploads an extension to the Chrome Web Store, disguising it as something useful (e.g., a “Free Coupons” or “PDF Converter” tool).

Crafted Data Injection

The extension includes code that submits carefully crafted HTML, JavaScript, or other data that Chrome’s extension engine doesn’t strictly validate.

Script Injection

When the extension displays a privileged Chrome page—or interacts with the browser—the attacker’s malicious content is inserted, bypassing typical protections.

Execution

Once in a privileged context, injected scripts can do all sorts of nasty things: steal cookies, read or change browser data, redirect traffic, or escalate extension capabilities.

Here’s a boiled-down JavaScript code snippet resembling a vulnerable pattern

// Background script in the extension
chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
    // Assume msg.html comes from an untrusted source e.g., a web page the extension interacts with
    // BAD: Inserts HTML directly without validation!
    document.getElementById('privileged-content').innerHTML = msg.html;
    sendResponse({status: "done"});
});

What's wrong here?
The code takes whatever comes in via msg.html and plops it right into a privileged content area of a browser page. If msg.html contains <script> tags or dangerous HTML, it will execute as if it’s trusted code. No input cleansing, no escaping!

With this flaw, if the extension is running in the context of a privileged page, it can be tricked into running arbitrary code.

`json

{ "html": "" }

The browser injects and runs this script in a privileged page context.

5. Victim’s private extension pages, browsing activity, or sensitive data can now be stolen or manipulated.

What Did Google Do?

Google patched this bug in Chrome 115..579.170. The fix? They added better data validation and escaping when extensions try to inject content into privileged pages. Now, any data passed to privileged contexts must be sanitized—it won’t just blindly load dangerous tags or scripts.

Update Chrome Regularly: Make sure you’re running Chrome version 115..579.170 or later.

- Be Careful with Extensions: Only install extensions you *really* need, and check reviews and permissions.
- Developers: Always validate and sanitize user-supplied content before injecting it into your extension's UI.

More Information & References

- Chromium Issue Tracker: 1461692 (CVE-2023-4077)
- Chrome Release Notes for Stable Channel Update
- CVE Details for CVE-2023-4077

Conclusion

CVE-2023-4077 serves as a critical lesson: anything passing through a browser extension—even if it’s optional, rare, or “internal”—must be sanitized. With Chrome’s global reach, even medium-severity bugs can have big security implications. Always stay patched, stick to safe browsing practices, and remember: extensions can be just as dangerous as any downloaded program.

Stay safe out there! 🚦

*If you found this post helpful, share it with your tech friends to raise awareness of browser extension risks!*

Timeline

Published on: 08/03/2023 01:15:00 UTC
Last modified on: 08/12/2023 06:21:00 UTC