I am having the identical problem with Firefox spawning almost 200 processes upon Firefox shutdown. I am using Win7Pro x64, so this is not just an issue in Windows 10. The problems exiting Firefox started with the 112.0.0 update. After the 112.0.0 update, exiting Firefox would spawn multiple "Crash Reporter" windows. This would continue until I closed them all. After the 112.0.1 update is when I first began to notice the issue with Firefox spawning up to 200 processes and 100% CPU upon exiting. I have tried opening Firefox in troubleshooting mode as well as tried using a different user profile, but this exiting issue continues.

Thanks in advance for assistance in solving this.

Do either or both of you have Firefox set to clear cookies and site data, and/or other history, when it closes? That didn't used to require a lot of processes, but maybe a bug was introduced somehow.

(Otherwise, it's difficult to think of anything interesting that Firefox does at shutdown.)

Do either or both of you have Firefox set to clear cookies and site data, and/or other history, when it closes?

Yes. I am using private mode at all times. One thing that isn't cleared upon exit is site preferences. It also happens when there isn't much to clear, like when I browse 1-3 websites when it couldn't gather much cookies etc.

I use Firefox in... "normal?" mode and I do NOT clear anything upon exiting Firefox. I use "custom" settings in "tracking prevention" and block all "cross-site cookies".

I have found what the problem is: Its because of number of cookie exceptions. I have over 150 of them. If I remove permissions.sqlite file in my profile folder, everything is back to normal (of course I would want to keep them).

Is there any way to get that info to Firefox developers, so they could look at it?

There might be a bug on file about this, but I didn't bookmark it so I can't refer you to it right away.

I have about 75 "Allow" exceptions (because other cookies are deleted at shutdown) and I haven't noticed a major change with Firefox 112. That said, with over 30 windows open most of the time, I'm used to things taking a while to start up and settle down...

By the way, to search for bugs you can either use a site-targeted search in Google or go directly to Bugzilla:

• https://bugzilla.mozilla.org/
• Google: shut-down site:bugzilla.mozilla.org (Jan 1, 2023 – Dec 31, 2023)

Thank you. I will create new bug, I can't find anything related when searching "cookie exceptions" or permissions.sqlite.

I can confirm that in my case, I have far more than 200 cookie "exceptions". I haven't experimented with the permissions file because I do not want to lose the "allow" and "block" cookies.

Thank you, and keep me posted!

I have opened a bug report here: https://bugzilla.mozilla.org/show_bug.cgi?id=1831166

I use Firefox in... "normal?" mode and I do NOT clear anything upon exiting Firefox. I use "custom" settings in "tracking prevention" and block all "cross-site cookies".

I can confirm that in my case, I have far more than 200 cookie "exceptions". I haven't experimented with the permissions file because I do not want to lose the "allow" and "block" cookies.

Just to confirm, your Firefox retains browsing history and persistent cookies normally from session to session, assuming the crashes didn't corrupt any files?

Could it be related to this bug about background tasks:

• 1827390 - Firefox 112: on exit looping to remove non-existent 'storage/to-be-removed' directory
• dom.quotaManager.backgroundTask.enabled = false

I do indeed retain history and cookies from session to session. I also do not clear cache on exit. As far as Firefox spawning hundreds of processes and 100% CPU usage upon exiting, this has not seemed to have corrupted any files, and Firefox starts fine the next time.

The "processes and CPU %" issue happens every time I close Firefox, and does not seem dependent on how long Firefox has been open nor dependent the web site(s) I had last visited.

"Crash Reports" are not generated every time Firefox closes; but every once in a while, multiple "Crash Reporter" windows will start to appear after I exit Firefox, and an additional crash report window will appear every 30 seconds or so until I either accept or dismiss them all. This behavior only occurs randomly upon exiting... anywhere from every 3rd to 6th time. This also seems to have started with the Version 112 update.

I rarely have more than 2 or 3 Firefox "tabs" open at one time. It's usually just one. I also rarely have more than 2 or 3 Windows programs running at the same time.

Hope this helps.

In my case everything is cleared out on exit except those site permissions. I use cookie exceptions list to allow cookies, because normally I block everything. And yeah, it only happens on exit, and it only happens because of what is stored in permissions.sqlite file, because moving it out fixes the issue, so I am assuming its because of how many of those cookie exceptions are on that list.

Does this also happen if you run Firefox in normal mode if you currently use Private Browsing mode?

Does this also happen if you run Firefox in normal mode if you currently use Private Browsing mode?

Yes. I have tried disabling private mode and like in wdunwoody's case the issue is still there in normal mode.

One experiment you could try is creating a new profile and replacing its permissions.sqlite file with the one that has your current exceptions.

New Profile Test

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it. You may want to bookmark this page for easy restarting.

Take a quick glance at the page and make a mental note of which Profile has this notation: This is the profile in use and it cannot be deleted. That is your current default profile.

Click the "Create a New Profile" button, then click Next. Assign a name like Test2023, ignore the option to relocate the profile folder, and click the Finish button.

Firefox will switch your default profile to the new one, so click the Set as Default Profile button for your regular one to avoid an unwanted surprise at your next startup.

Scroll down to Test2023 and click its Launch profile in new browser button.

Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to get a clean test.

Turn on automatic private browsing.

Does shutdown work normally in the new profile?

Back on the about:profiles page, use the Root Directory link for Test2023 to open the profile folder so you can replace permissions.sqlite and repeat the Launch / shutdown test.

Does shutdown work normally in the new profile with the populated permissions.sqlite database?

One experiment you could try is creating a new profile and replacing its permissions.sqlite file with the one that has your current exceptions.

I forgot to mention it here, but I have already did that. It works the same with the new profile. So it must be how Firefox handles permissions.sqlite file. I have posted some more info on bugzilla here.

Okay, after testing, I agree with cor-el's comment that this appears to be the same bug as 1827390 which is fixed in the beta of Firefox 113, which is due out Tuesday. I'll explain my logic in the bug.

In summary, the problem in Firefox 112 appears to be caused specifically by "Allow for Session" cookie permissions because Firefox is running a background task to remove site data (offline storage folders) for those sites at shutdown.

The thing with site data is that there is only one folder named "to-be-removed" and Firefox removes it for the first Allow for Session permission. Doing that again for every additional Allow for Session permissions is wasteful, and those attempts seem to be failing very slowly so the wasted processes take a long time to clear.

Firefox 113 fixed that, although it might have been a Band-Aid fix that will get revised in the future when related bugs are worked on.