CVE-2026-35208 lichess.org has an Unsanitized Stream Title Injection on /streamer
Approved streamers can inject arbitrary HTML into the streamer page and homepage widget via unsanitized stream titles, bypassing CSP restrictions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-35208?
CVE-2026-35208 is a medium-severity cross-site scripting vulnerability in lichess-org lila, published on 6 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
lichess.org is the forever free, adless and open source chess server. Any approved streamer can inject arbitrary HTML into /streamer and the homepage “Live streams” widget by placing markup in their Twitch/YouTube stream title. CSP is present and blocks inline script execution, but the issue is still a server-side HTML injection sink. To trigger this, a Lichess account only needs to satisfy the normal streamer requirements and get approved. Per Streamer.canApply, that means an account older than 2 days with at least 15 games, or a verified/titled account. After moderator approval, once the streamer goes live, Lichess pulls the platform title and renders it into the UI as-is. No extra privileges are needed beyond a normal approved streamer profile. This vulnerability is fixed with commit 0d5002696ae705e1888bf77de107c73de57bb1b3.
Which versions are affected by CVE-2026-35208?
It affects 1 product.
Products include Lichess Lila.
How do I fix CVE-2026-35208?
No fix has been published for CVE-2026-35208 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-35208 being exploited?
There is no known exploitation of CVE-2026-35208 in the wild and no public exploit code.
Other vulnerabilities in lichess-org lila
Sources
Also known as GHSA-v7gh-939r-pfjq.