Debian: DSA-5026-1 Critical: Firefox-ESR Arbitrary Code Execution

Multiple security issues have been found in the Mozilla Firefox
web browser, which could potentially result in the execution
of arbitrary code, information disclosure or spoofing.

Debian follows the extended support releases (ESR) of Firefox. Support
for the 78.x series has ended, so starting with this update we're now
following the 91.x releases.

Between 78.x and 91.x, Firefox has seen a number of feature updates. For
more information please refer to
https://www.firefox.com/en-US/firefox/91.0esr/releasenotes/?redirect_source=mozilla-org

For the oldstable distribution (buster) one more final toolchain update
is needed, updated packages will shortly be available as 91.4.1esr-1~deb10u1

For the stable distribution (bullseye), these problem have been fixed in
version 91.4.1esr-1~deb11u1.

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/source-package/firefox...