CVE-2020-6802

### Impact A [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. ### Patches v3.1.1 ### Workarounds * modify `bleach.clean` calls to not whitelist `noscript` and one or more of the following raw tags: ``` title textarea script style noembed noframes iframe xmp ``` * 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. ### References * https://bugzilla.mozilla.org/show_bug.cgi?id=1615315 * https://cure53.de/fp170.pdf * https://nvd.nist.gov/vuln/detail/CVE-2020-6802 * https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach ### Credits * Reported by [Yaniv Nizry](https://twitter.com/ynizry) from the CxSCA AppSec group at Checkmarx ### For more information If you have any questions or comments about this advisory: * Open an issue at [https://github.com/mozilla/bleach/issues](https://github.com/mozilla/bleach/issues) * Email us at [security@mozilla.org](mailto:security@mozilla.org)

In Mozilla Bleach before 3.11, a mutation XSS affects users calling bleach.clean with noscript and a raw tag in the allowed/whitelisted tags option.