You get tabs opening endlessly if you select Firefox as the application to handle a file when you get an "Open with" dialog. You will have to remove this action and never select Firefox in a download dialog.

• https://support.mozilla.org/en-US/kb/firefox-repeatedly-opens-empty-tabs-or-windows

Everything else opens fine, this is the first time I've had that issue. I'd think that it shouldn't be hard to code some error detection when it loops like that. Or just make it possible to abort. I tried 'Quit' but it restarted the same way. I with the 'Restore previous session' feature was there, I just don't have it. BTW it also downloaded several hundred zero length files to my download directory.

If it crashes more than twice in a row, it will start with about:sessionrestore where you can choose which tabs to restore. You can force a crash by terminating from the task manager.

Where's the task manager? It didn't take me to 'about:sessionrestore' , but then again I didn't do that official termination either. But it sounds like exactly the polite thing to do. As it was, with hundreds of open tabs I had to kill them all and lost several that I'd rather have kept.

BTW, why are there so many different versions of the main menu under the 'hamburger'? Some online helps show you a picture and mine resembles none that I've seen. Even when I restrict search to the last year (because things do change over time) still I get no match. This gets frustrating because, say, some online help says: 'select 'Session restore' from the main menu' -- but I have no session restore. Or: 'select Options' -- but I have no Options. And so on. That's why I'll ask you where 'termination' is -- If I go searching I'll get ten answers, none of which work.

The task manager is usually part of your linux distro but may go by different names, on Ubuntu GNOME it is "System Monitor".

Yup, there it is. in xfce: Accessories > Task Manager.