Is the problem with the warning that appears on the last/only Firefox window, in other words, when closing the window will exit out of Firefox, or on a second or third window with multiple tabs?

You can check these hidden preferences to get the settings you want:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste warn and pause while the list is filtered

(3) If the browser.tabs.warnOnClose preference is bolded and "user set" to false, double-click it to restore the default value of true (this should cover second/third window scenario)

(4) If the browser.warnOnQuit preference is bolded and "user set" to false, double-click it to restore the default value of true (this should cover the last/only window scenario)

On that #4, I never see that myself because I always shut down Firefox using the menu, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Maybe it's because Firefox is set to automatically show windows and tabs from the previous session at startup.

You only see the warning items in Options/Preferences when the related prefs have been changed directly on the about:config page. When the prefs have the default value then the check box items for the warnings are hidden.

What startup setting do you use?

If you use "Show my windows and tabs from last time" then Firefox doesn't show a warning when you close Firefox with multiple tabs open.

I did this and it's already set at "true".

Can you clarify what you are doing when you expect this warning to appear?

Is this with closing multiple tabs in a window or with closing a window (deliberately or by accident) with multiple tabs open?

Searched on-line and found out there was an "add on" called "Always Asked" that turned it back on. Why Firefox did away with something so obviously useful and kept the fix secret is beyond me.

Why is there so much of this in computers. Are they stupid or just arrogant?

Here's a link in case anyone is interested in trying it: https://addons.mozilla.org/firefox/addon/always-ask/

Apparently this is helpful to avoid accidentally shutting down Firefox and having to start it up again to continue your session. My guess is that the warning was turned off because other people who knew what they were doing found it annoying.

That's the one I was talking about that I found! I don't know why some computer ... always has undo things and cause so much needless ...!