What’s Vulnerable › Vulnerabilities

CVE-2020-6816

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-03-24 · updated 2026-06-17
• Weakness: CWE-79

Description

In Mozilla Bleach before 3.12, a mutation XSS in bleach.clean when RCDATA and either svg or math tags are whitelisted and the keyword argument strip=False.

Affected products

• Fedoraproject Fedora: 33
• Mozilla Bleach: before 3.1.2 — fixed in 3.1.2

How to fix

Upgrade to a fixed version: Mozilla Bleach 3.1.2. Check the vendor advisory for mitigations.

References

• https://advisory.checkmarx.net/advisory/CX-2020-4277
• https://github.com/mozilla/bleach/security/advisories/GHSA-m6xf-fq7q-8743
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EDQU2SZLZMSSACCBUBJ6NOSRNNBDYFW5/
• https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach
• https://advisory.checkmarx.net/advisory/CX-2020-4277
• https://github.com/mozilla/bleach/security/advisories/GHSA-m6xf-fq7q-8743
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EDQU2SZLZMSSACCBUBJ6NOSRNNBDYFW5/
• https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach

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