Until yesterday Debian “stable” came with Firefox ESR 78, a browser that has been unsupported by Mozilla since October 5, 2021. This lead to concerned discussions.
Now it was finally replaced by Firefox ESR 91, along with a security advisory urging users to upgrade, listing no fewer than 17 Common Vulnerabilities and Exposures (CVEs).
The delay was apparently due to toolchain issues with rustc, a compiler required to build Firefox from source code. Kudos to the package maintainers who worked hard to resolve these problems, which is tracked here!
I upgraded tonight:
$ sudo apt update; sudo apt upgrade
[..]
Get:1 http://security.debian.org/debian-security bullseye-security/main amd64 firefox-esr amd64 91.4.1esr-1~deb11u1 [58.7 MB]
[..]
Unpacking firefox-esr (91.4.1esr-1~deb11u1) over (78.15.0esr-1~deb11u1) ...
[..]
Setting up firefox-esr (91.4.1esr-1~deb11u1) ...
Besides the security fixes it looks like Mozilla has once again opted for further flattening the appearance of UI elements.
What else is new: https://www.mozilla.org/en-US/firefox/91.0esr/releasenotes/

