User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0

Steps to reproduce:

A window was open with some tabs.
An available update was downloaded (the menu icon had the green update icon).
A new tab is open via an external program or by the command line.

Actual results:

The updater window appears, and it apparently install a new version.
The new tab is opened, but it does not work.
The other tabs also stop working.

Expected results:

The updater should not be run and the new tab should be opened directly.

I noticed that it started a few days ago.

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0

I'm not sure if this is right.
The about page says my current version is "67.0a1 (2019-03-11) (64-bit)".

Dave, I suspect that this could be due to the recent changes to how startup is handled. I am fairly certain that if there was a running instance and there was a pending update we wouldn't hit ProcessUpdates in nsAppRunner.cpp on Linux.
https://searchfox.org/mozilla-central/source/toolkit/xre/nsAppRunner.cpp#3926

Looks like this affects Windows as well though no crash and tabs worked, etc.

I filed bug 1534508 for the startup issue that is causing this.

Verified that bug 1534508 and hence this bug isn't present using a release build

Looks like this affects Windows as well though no crash and tabs worked, etc.

I've just checked it again after it installed a new update.
The old task still work, but they looked much slower.
I probably confused it.

However, the new tabs don't load.

I also noticed that the bug title is misleading.
It does not crash literally, as the window stays open, but it cannot be used for new tabs and keep navigating the web.

This is fixed for me now that bug 1534508 has landed.

If there are still cases where this bug isn't fixed please file a new bug. Thanks!

It fixed it for me too.

Thank you.