lichess.org has an Unsanitized Stream Title Injection on /streamer

{
  "id": "1a224163579346cacfa7ba761c7eec27a5bc071e7c42fc745447d42703738eb2",
  "url": "https://osv.dev/vulnerability/CVE-2026-35208",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "lichess.org has an Unsanitized Stream Title Injection on /streamer",
    "summary": "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.",
    "evidence": "osv:CVE-2026-35208",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-35208",
      "aliases": [
        "CVE-2026-35208",
        "GHSA-v7gh-939r-pfjq"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/lichess-org/lila",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0d5002696ae705e1888bf77de107c73de57bb1b3"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0d5002696ae705e1888bf77de107c73de57bb1b3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0d5002696ae705e1888bf77de107c73de57bb1b3"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "pre-responsive",
            "pre-bcrypt",
            "v1.1.0",
            "v1.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-35208.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.293135249Z",
      "provider": "osv",
      "references": [
        "https://vimeo.com/1175908262",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35208.json",
        "https://github.com/lichess-org/lila/security/advisories/GHSA-v7gh-939r-pfjq",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-35208",
        "https://github.com/lichess-org/lila/commit/0d5002696ae705e1888bf77de107c73de57bb1b3"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-116",
          "CWE-79"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35208.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-35208",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518877,
  "published_at": "2026-04-06T20:06:25.821+00:00"
}