CVE-2026-126800: Hydro @hydrooj/ui-default before 4.59.1 Stored XSS via Markdown language- Class
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.
Event History
Frequently Asked Questions
Who can exploit this vulnerability, and who is at risk when it is triggered?
Any registered user can store a malicious payload in a profile bio. The payload executes when an administrator or another user views that bio, placing those viewers' sessions at risk.
What does an attacker need to exploit it?
The attacker needs a registered account and must be able to place double quotes in language- class tokens in Markdown content. Exploitation also requires a target user to view the stored profile bio.
What data can be compromised through a successful attack?
The injected script can steal a viewer's non-httpOnly sid session cookie. An attacker can use that cookie for session hijacking.
Which versions should be remediated?
Hydro @hydrooj/ui-default versions before 4.59.1 are affected. Upgrade to version 4.59.1 or later.