medium
6.1
CWE
79
Advisory Published
CVE Published
Updated

CVE-2020-6802: XSS

First published: Mon Feb 24 2020(Updated: )

### 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)

Credit: security@mozilla.org security@mozilla.org

Affected SoftwareAffected VersionHow to fix
pip/bleach<3.1.1
3.1.1
Mozilla Bleach<3.1.1
Red Hat Fedora=30
Red Hat Fedora=31
Red Hat Fedora=32

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Reference Links

Frequently Asked Questions

  • What is the severity of CVE-2020-6802?

    CVE-2020-6802 is considered a moderate vulnerability, specifically a mutation XSS that can affect user input validation in certain contexts.

  • How do I fix CVE-2020-6802?

    To fix CVE-2020-6802, upgrade to Bleach version 3.1.1 or later.

  • What software is impacted by CVE-2020-6802?

    CVE-2020-6802 affects Bleach version 3.1.1 and earlier as well as several Fedora releases including versions 30, 31, and 32.

  • What workaround exists for CVE-2020-6802?

    A workaround for CVE-2020-6802 is to modify calls to bleach.clean to avoid whitelisting the noscript tag.

  • Is user data at risk due to CVE-2020-6802?

    Yes, user data is at risk as CVE-2020-6802 allows for potential XSS attacks through improper validation of input when using whitelisted tags.

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