{"id":"GHSA-q65m-pv3f-wr5r","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","aliases":["CVE-2020-6802","PYSEC-2020-27"],"modified":"2026-05-07T05:02:10.534670391Z","published":"2020-02-24T17:33:44Z","database_specific":{"nvd_published_at":"2020-03-24T22:15:00Z","cwe_ids":["CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2020-02-19T19:43:47Z"},"references":[{"type":"WEB","url":"https://github.com/mozilla/bleach/security/advisories/GHSA-q65m-pv3f-wr5r"},{"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://advisory.checkmarx.net/advisory/CX-2020-4276"},{"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"},{"type":"WEB","url":"https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach"}],"affected":[{"package":{"name":"bleach","ecosystem":"PyPI","purl":"pkg:pypi/bleach"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.1"}]}],"versions":["0.1","0.1.1","0.1.2","0.2","0.2.1","0.2.2","0.3","0.3.1","0.3.3","0.3.4","0.5.0","0.5.1","1.0.0","1.0.1","1.0.2","1.0.3","1.0.4","1.1.0","1.1.1","1.1.2","1.1.3","1.1.4","1.1.5","1.2","1.2.1","1.2.2","1.4","1.4.1","1.4.2","1.4.3","1.5.0","2.0.0","2.1","2.1.1","2.1.2","2.1.3","2.1.4","3.0.0","3.0.1","3.0.2","3.1.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2020/02/GHSA-q65m-pv3f-wr5r/GHSA-q65m-pv3f-wr5r.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"}]}