TinaCMS admin preview iframe loads an attacker-controlled origin from the URL fragment

{
  "id": "1216efd5a7424bf1b77eeb0d7bcf6bc611303fa0ffe4e47f48bfab135fe799dd",
  "url": "https://osv.dev/vulnerability/GHSA-x34j-47hf-4xg7",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "TinaCMS admin preview iframe loads an attacker-controlled origin from the URL fragment",
    "summary": "### Summary The TinaCMS admin builds its preview `` from the `/~/*` hash-router splat without checking that the value stays same-origin. A fragment with a doubled slash (`#/~//attacker.example/p`) becomes the protocol-relative URL `//attacker.example/p`, so the admin frames an external site. That same unvalidated string derives `expectedOrigin`, the only trust anchor for the admin↔preview `postMessage` channel, so the attacker's frame is treated as trusted: it can submit any GraphQL operation, which the admin executes with the signed-in editor's token and posts back to the attacker's origin. One link, opened by a logged-in editor, gives an unauthenticated remote attacker arbitrary read and write access to the site's content API as that editor. ### Details Root cause — the router splat becomes the frame source with no same-origin check: ``` packages/tinacms/src/admin/index.tsx:16 HashRouter as Router, packages/tinacms/src/admin/index.tsx:329 path='/~/*' packages/tinacms/src/admin/index.tsx:173 const [url, setURL] = React.useState(`/${params['*']}`); packages/tinacms/src/admin/index.tsx:176 const paramURL = `/${params['*']}`; packages/@tinacms/app/src/preview.tsx:24 src={props.url} ``` The leading `/` is meant to force a relative path, but `react-router-dom@6.30.3` returns the splat with its own leading slash for `/~//x`, producing `//x`. The iframe has no `sandbox` attribute and the admin bundle ships no CSP. The trust anchor is then computed from that same value: ``` packages",
    "evidence": "osv:GHSA-x34j-47hf-4xg7",
    "products": [
      {
        "name": {
          "value": "tinacms",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.14.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "@tinacms/app",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.5.14",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "GHSA-x34j-47hf-4xg7",
      "aliases": [
        "CVE-2026-108261",
        "GHSA-x34j-47hf-4xg7"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.14.0"
                }
              ]
            }
          ],
          "package": {
            "name": "tinacms",
            "purl": "pkg:npm/tinacms",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-x34j-47hf-4xg7/GHSA-x34j-47hf-4xg7.json",
            "last_known_affected_version_range": "<= 3.13.0"
          }
        },
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.5.14"
                }
              ]
            }
          ],
          "package": {
            "name": "@tinacms/app",
            "purl": "pkg:npm/%40tinacms/app",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-x34j-47hf-4xg7/GHSA-x34j-47hf-4xg7.json",
            "last_known_affected_version_range": "<= 2.5.13"
          }
        }
      ],
      "modified": "2026-10-09T21:15:05.360447760Z",
      "provider": "osv",
      "references": [
        "https://github.com/tinacms/tinacms/security/advisories/GHSA-x34j-47hf-4xg7",
        "https://github.com/tinacms/tinacms/pull/7522",
        "https://github.com/tinacms/tinacms/commit/b57dbf4b56201aef15cd92caa49fd12ab96bbecf",
        "https://github.com/tinacms/tinacms",
        "https://github.com/tinacms/tinacms/releases/tag/@tinacms/app@2.5.14",
        "https://github.com/tinacms/tinacms/releases/tag/tinacms@3.14.0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-346",
          "CWE-441",
          "CWE-601"
        ],
        "severity": "CRITICAL",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-09T20:56:48Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-108261",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 124258,
  "published_at": "2026-10-09T20:56:48+00:00"
}