CVE-2022-31743

What it actually does

Incorrect HTML comment parsing in Firefox allows user-controlled data placed inside comments to break out and inject executable script, enabling cross-site scripting that differs from other browsers' behavior.

Why it matters to the business

Attackers could run unauthorized code in users' browsers on affected sites, potentially stealing session data or performing actions as the user; however the issue is old with minimal exploitation activity so operational risk remains low for updated environments.

How an attack unfolds

An attacker supplies crafted input containing HTML comment sequences that the vulnerable parser mishandles, causing injected script to execute when the page renders in an unpatched Firefox browser; no named threat actors or ransomware campaigns have been observed leveraging this flaw.

How to fix it

Upgrade Mozilla Firefox to version 101 or later; enable automatic updates and audit any internal web applications that reflect data inside HTML comments.

How to confirm the fix worked

Verify installed Firefox version is 101 or higher; attempt reproduction with test payloads that place script inside comments and confirm the script does not execute.

Typical attack path

1. Locate a web application that places attacker-controlled data inside HTML comments
2. Craft input that uses the parser discrepancy to terminate the comment early and inject script tags
3. Deliver the payload via a link or form submission to a victim using vulnerable Firefox
4. Script executes in the victim's browser context with the site's origin

How to detect it

Examine web server access logs and application logs for unusual comment payloads containing script tags or HTML entities that attempt to break out of comments; review browser telemetry or proxy logs for visits to suspect pages around the time of any reported anomalous behavior.

What your security team should do

• Prioritize deployment of Firefox 101+ across all managed systems
• Scan web applications for user data rendered inside HTML comments and refactor to safer output encoding
• Review browser update policies and enforce automatic updates to reduce exposure windows on legacy issues