Hydro @hydrooj/ui-default before 4.59.1 Stored XSS via Markdown language- Class
Not on CISA's list of exploited flaws, and not in the news we track.
9.3of 10, critical
Reading the vendor advisory
Fix it in your code
Each opens with a short prompt that points at Global Hack Map's public runbook for CVE-2026-126800. Nothing runs until you send it.
Hydro @hydrooj/ui-default before 4.59.1 contains a stored cross-site scripting vulnerability that allows registered users to inject script by placing double quotes in language- class tokens within markdown-it-xss.ts. Attackers can store a payload in their profile bio that executes when administrators or other users view it, stealing the non-httpOnly sid session cookie for session hijacking.
You are affected if
The fix