A firefox-esr security update has been released for Debian GNU/Linux 10 to address multiple security issues.

DSA 4768-1: firefox-esr security update

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Debian Security Advisory DSA-4768-1 security@debian.org
  https://www.debian.org/security/ Moritz Muehlenhoff
September 28, 2020   https://www.debian.org/security/faq
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Package : firefox-esr
CVE ID : CVE-2020-15673 CVE-2020-15676 CVE-2020-15677 CVE-2020-15678

Multiple security issues have been found in the Mozilla Firefox web
browser, which could potentially result in the execution of arbitrary
code, cross-site scripting or spoofing the origin of a download.

Debian follows the extended support releases (ESR) of Firefox. Support
for the 68.x series has ended, so starting with this update we're now
following the 78.x releases.

Between 68.x and 78.x, Firefox has seen a number of feature updates.
For more information please refer to
  https://www.mozilla.org/en-US/firefox/78.0esr/releasenotes/

For the stable distribution (buster), these problems have been fixed in
version 78.3.0esr-1~deb10u1.

We recommend that you upgrade your firefox-esr packages.

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

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/