---
id: CVE-2020-6802
aliases:
  - GHSA-q65m-pv3f-wr5r
  - PYSEC-2020-27
title: XSS in Bleach when noscript and raw tag whitelisted
summary: XSS in Bleach when noscript and raw tag whitelisted
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
vendor: bleach
product: bleach
ecosystem: pip
affected:
  - bleach < 3.1.1
patched:
  - bleach 3.1.1
published: '2020-02-24'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-q65m-pv3f-wr5r'
references:
  - url: 'https://github.com/mozilla/bleach/security/advisories/GHSA-q65m-pv3f-wr5r'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2020-6802'
  - url: >-
      https://github.com/mozilla/bleach/commit/f77e0f6392177a06e46a49abd61a4d9f035e57fd
  - url: 'https://advisory.checkmarx.net/advisory/CX-2020-4276'
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1615315'
  - url: 'https://cure53.de/fp170.pdf'
  - url: 'https://github.com/mozilla/bleach'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/bleach/PYSEC-2020-27.yaml
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/72R4VFFHDRSQMNT7IZU3X2755ZP4HGNI
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OCNLM2MGQTOLCIVVYS2Z5S7KOQJR5JC4
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YTULPQB7HVPPYWEYVNHJGDTSPVIDHIZX
  - url: >-
      https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach
tags:
  - osv
  - pip
epss: 0.01731
epssPercentile: 0.76629
ingestedAt: '2026-07-08T18:25:52.106Z'
---

## Overview

### 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)


## Affected packages

- `bleach < 3.1.1`

## Remediation

Upgrade to a patched release:

- `bleach 3.1.1`