Firefox background update 74.0 to 74.0.1 prevents using any active tab

[Andrew]

I opened several new tabs via context menu, then when switching to one of those new tabs was presented with the "Firefox must be restarted to continue" type message when an update had been applied in the background. On attempt to switch back to an already active tab in order to securely close existing site sessions, form submissions, etc. before restarting Firefox, I found that I was unable to use existing tabs.

Problem presented as the newly opened tab was not rendering any page (completely white). Clicking any existing tab would not switch from the newly opened tab. Clicking on "help - troubleshooting information" and "help - submit feedback" opened those tabs in the background but alas was not able to switch to those tabs to view them.

I think this is a bug and user should be able to continue to use existing tabs to complete their existing sessions when a Firefox background update has been applied.

[Andrew (am-public-o)]

Added screenshot that was taken while experiencing the issue

[Andrew (am-public-o)]

$uname -a
Linux {host} 5.3.0-45-generic #37-Ubuntu SMP Thu Mar 26 20:41:27 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=19.10
DISTRIB_CODENAME=eoan
DISTRIB_DESCRIPTION="Ubuntu 19.10"

[Olivier Tilloy (osomon)]

I attempted to reproduce the problem by downgrading firefox in a 20.04 VM, clearing the profile directory, running the old version and opening a few tabs on various different sites, then upgrading to the latest version in the Ubuntu archive while the old version was still running with all the tabs open. But the running instance continued to work normally, and I didn't get any notification (in firefox) that an update had been installed.

apt did warn me on the console, though:

    Please restart all running instances of firefox, or you will experience problems.

[Olivier Tilloy (osomon)]

Somewhat related: bug #1834217.