A python-bleach security update has been released for Debian GNU/Linux 10 to address a mutation XSS vulnerability in bleach.clean when strip=False and 'math' or 'svg' tags and one or more of the RCDATA tags were whitelisted.

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Debian Security Advisory DSA-4643-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
March 20, 2020   https://www.debian.org/security/faq
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Package : python-bleach
CVE ID : CVE-2020-6816
Debian Bug : 954236

It was reported that python-bleach, a whitelist-based HTML-sanitizing
library, is prone to a mutation XSS vulnerability in bleach.clean when
strip=False and 'math' or 'svg' tags and one or more of the RCDATA tags
were whitelisted.

For the stable distribution (buster), this problem has been fixed in
version 3.1.2-0+deb10u1.

We recommend that you upgrade your python-bleach packages.

For the detailed security status of python-bleach please refer to its
security tracker page at:
  https://security-tracker.debian.org/tracker/python-bleach

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/