{"id":"CVE-2020-6802","aliases":["GHSA-q65m-pv3f-wr5r","PYSEC-2020-27"],"url":"https://o3.security/vulnerability/CVE-2020-6802","summary":"XSS in Bleach when noscript and raw tag whitelisted","details":"### Impact\n\nA [mutation XSS](https://cure53.de/fp170.pdf) affects users calling `bleach.clean` with `noscript` and a raw tag (see below) in the allowed/whitelisted tags option.\n\n### Patches\n\nv3.1.1\n\n### Workarounds\n\n* modify `bleach.clean` calls to not whitelist `noscript` and one or more of the following raw tags:\n\n```\ntitle\ntextarea\nscript\nstyle\nnoembed\nnoframes\niframe\nxmp\n```\n\n* A strong [Content-Security-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP) without `unsafe-inline` and `unsafe-eval` [`script-src`s](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src)) will also help mitigate the risk.\n\n### References\n\n* https://bugzilla.mozilla.org/show_bug.cgi?id=1615315\n* https://cure53.de/fp170.pdf\n* https://nvd.nist.gov/vuln/detail/CVE-2020-6802\n* https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach\n\n### Credits\n\n* Reported by [Yaniv Nizry](https://twitter.com/ynizry) from the CxSCA AppSec group at Checkmarx\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\n* Open an issue at [https://github.com/mozilla/bleach/issues](https://github.com/mozilla/bleach/issues)\n* Email us at [security@mozilla.org](mailto:security@mozilla.org)\n","published":"2020-03-24T22:15:12.563Z","modified":"2026-10-20T10:54:23.366288176Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":2,"affectedPackages":[{"ecosystem":"PyPI","name":"bleach","fixedVersion":"3.1.1"}],"fix":{"url":"https://github.com/mozilla/bleach/commit/f77e0f6392177a06e46a49abd61a4d9f035e57fd","label":"mozilla/bleach@f77e0f6"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/72R4VFFHDRSQMNT7IZU3X2755ZP4HGNI/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OCNLM2MGQTOLCIVVYS2Z5S7KOQJR5JC4/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YTULPQB7HVPPYWEYVNHJGDTSPVIDHIZX/"},{"type":"ADVISORY","url":"https://github.com/mozilla/bleach/security/advisories/GHSA-q65m-pv3f-wr5r"},{"type":"EVIDENCE","url":"https://advisory.checkmarx.net/advisory/CX-2020-4276"},{"type":"EVIDENCE","url":"https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-6802"},{"type":"WEB","url":"https://github.com/mozilla/bleach/commit/f77e0f6392177a06e46a49abd61a4d9f035e57fd"},{"type":"WEB","url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1615315"},{"type":"WEB","url":"https://cure53.de/fp170.pdf"},{"type":"PACKAGE","url":"https://github.com/mozilla/bleach"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/bleach/PYSEC-2020-27.yaml"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/72R4VFFHDRSQMNT7IZU3X2755ZP4HGNI"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OCNLM2MGQTOLCIVVYS2Z5S7KOQJR5JC4"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YTULPQB7HVPPYWEYVNHJGDTSPVIDHIZX"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:54:23.366288176Z"}}