Chrome is one of the most trusted and widely used web browsers, but even Google’s top engineers can make mistakes. One such slip, tracked as CVE-2022-0801, was a bug in Chrome’s HTML parser that could let remote attackers bypass its built-in protections against Cross-Site Scripting (XSS). This flaw was present in Chrome before version 99..4844.51.
In this post, we’ll talk about what CVE-2022-0801 actually was, how it worked, and why it mattered for anyone surfing the web on Chrome. We’ll also look at a code snippet that shows how an attacker might have exploited this bug, with links to trusted sources at the end.
CVE-2022-0801 is officially described as
> Inappropriate implementation in HTML parser in Google Chrome prior to 99..4844.51 allowed a remote attacker to bypass XSS preventions via a crafted HTML page. (Chrome security severity: Medium)
Breaking that down
- “Inappropriate implementation in HTML parser”: The code that reads and processes HTML was not handling some situations the right way.
- “Allowed a remote attacker to bypass XSS preventions”: Hackers could create a specially crafted web page that lets them sneak past Chrome’s protections against XSS.
- “Via a crafted HTML page”: The attack starts when a victim visits a specific web page designed by the hacker.
How the Bug Happened (Simplified)
The HTML parser is the part of Chrome that turns the HTML code from websites into the pages you see. For security, there are rules in the parser to help block malicious scripts (XSS).
With CVE-2022-0801, there was a logic mistake or missing rules that allowed certain HTML and JavaScript combinations to sneak through. A cyber attacker could build an HTML page to take advantage of this and run unwanted code on your browser — defeating Chrome’s XSS defenses.
Example Exploit (Code Snippet)
Here’s a simple (and sanitized) example of what the exploit might look like. The real code may have been more complex, but this will help give you the idea.
Suppose Chrome was supposed to block event handler attributes like onerror, but due to this bug, an attacker could use a broken HTML tag so Chrome’s parser gets confused:
<!-- This is how a normal browser should handle the tag -->
<img src="invalid.jpg" onerror="alert('XSS');">
<!-- Attacker craft: Trick Chrome’s parser by splitting the tag -->
<scr<script>ipt>
alert('XSS');
</scr</script>ipt>
Or by using newlines, special Unicode characters, or malformed nesting, the parser could miss the malicious code.
When someone visited a page with this code, the attacker’s script could run in the context of trusted websites — stealing data, cookies, or impersonating the victim.
Build a Webpage: Attacker creates a specially crafted HTML file with bypass payload.
2. Host the Webpage: The attacker puts it somewhere victims are likely to visit, such as compromised forums or by sending phishing links.
User Visits Page: If user’s Chrome is below 99..4844.51, the browser misparses the page.
4. Bypass XSS Filter: The malicious JavaScript runs, even though Chrome would normally have stopped it.
5. Attacker Gains Access: The attacker can now do whatever their script allows — often stealing login credentials or session cookies.
Why This Matter
Cross-Site Scripting is one of the most common and dangerous web attacks. Browser-side XSS filters are the last line of defense when website owners don’t fully sanitize user data. This bug made Chrome users vulnerable, even on sites where protections should have helped.
If you’re a developer, always keep browsers updated and validate/sanitize input on the server. Never count on the browser alone to protect you!
Links to Official References
- Chrome Release Note: 99..4844.51
- Chromium Issue Tracker for CVE-2022-0801
- CVE-2022-0801 entry at NVD
Final Thoughts
Software bugs like CVE-2022-0801 are always a reminder that nobody is perfect — not even Google. But the web is safer because security researchers report these problems, and browsers like Chrome fix them fast. Always keep your browser up to date, and if you’re building web apps, remember: trust no input!
If you want to get into detail, check out the official bug tracker and release notes linked above. Stay safe online!
Timeline
Published on: 01/02/2023 23:15:00 UTC
Last modified on: 01/09/2023 19:17:00 UTC