{"id":"CVE-2021-21320","aliases":["GHSA-52mq-6jcv-j79x"],"url":"https://o3.security/vulnerability/CVE-2021-21320","summary":"User content sandbox can be confused into opening arbitrary documents","details":"### Impact\n\nThe user content sandbox can be abused to trick users into opening unexpected documents after several user interactions. The content can be opened with a `blob` origin from the Matrix client, so it is possible for a malicious document to access user messages and secrets.\n\n### Patches\n\nThis has been fixed by https://github.com/matrix-org/matrix-react-sdk/pull/5657, which is included in 3.15.0.\n\n### Workarounds\n\nThere are no known workarounds.","published":"2021-03-02T03:15:13.213Z","modified":"2026-10-20T10:53:33.513937893Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"matrix-react-sdk","fixedVersion":"3.15.0"}],"fix":{"url":"https://github.com/matrix-org/matrix-react-sdk/commit/b386f0c73b95ecbb6ea7f8f79c6ff5171a8dedd1","label":"matrix-org/matrix-react-sdk@b386f0c"},"references":[{"type":"ADVISORY","url":"https://github.com/matrix-org/matrix-react-sdk/security/advisories/GHSA-52mq-6jcv-j79x"},{"type":"ADVISORY","url":"https://www.npmjs.com/package/matrix-react-sdk"},{"type":"FIX","url":"https://github.com/matrix-org/matrix-react-sdk/commit/b386f0c73b95ecbb6ea7f8f79c6ff5171a8dedd1"},{"type":"FIX","url":"https://github.com/matrix-org/matrix-react-sdk/pull/5657"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21320"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:53:33.513937893Z"}}