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.
CVSS Score
5.3
EPSS Score
0.0
Published
2026-04-06
Lichess lila before commit 11b4c0fb00f0ffd823246f839627005459c8f05c (2025-06-02) contains a Server-Side Request Forgery (SSRF) vulnerability in the game export API. The players parameter is passed directly to an internal HTTP client without validation, allowing remote attackers to force the server to send HTTP requests to arbitrary URLs
CVSS Score
6.5
EPSS Score
0.002
Published
2025-11-13