Hi roberto32, this is an unusual scenario.

At this point, I would NOT remove any profiles.

I think you will eventually need to close your regular Firefox. But before closing it, can you confirm it is version 78.0.1 and its installation location by checking the Troubleshooting Information page? Either:

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

The first table on the page under the Application Basics header should show

• Version
• Application Binary (location of the program folder)

The Application Binary typically is one of these:

• C:\Program Files\Mozilla Firefox\firefox.exe
• C:\Program Files (x86)\Mozilla Firefox\firefox.exe -- folder inherited from 32-bit Firefox back in the day

Sometimes you end up with Firefox installed in both folders, and we may need to remove the unwanted one, so we should be confident of where the "good one" is.

The next time you exit Firefox and restart it, is it the correct version, and does it select the correct profile?

Thanks for the quick response.

From the Troubleshooting Information page, I get:

• version 78.0.1
• Application Binary is located in C:\Program Files\Mozilla Firefox\firefox.exe (NB: created 19 June 2019, modified 30 June 2020)
• BUT, there is also a Firefox.exe in C:\Program Files (x86)\Mozilla Firefox (NB: created 19 May 2018, modified today, 6 July 2020)

Naturally I'm reluctant to close the FF that's now open and have it then re-open minus passwords, bookmarks and everything else. For safety, I have made backups of my current profile (including logins.json), but then if the worst happens - i.e. FF reopens with a virgin profile - would simply pasting logins.json into the profile folder be enough to restore the passwords?

I see this extra profile issue discussed here but the answer there (to keep both profiles and choose between them) sounds dangerous. I'm happy with the (single) profile I already have and not happy with the unwelcome guest.

You can check the compatibility.ini file is each profile for the file path of the Firefox version that last used the profile.

Checked comptability.ini, results:

• jn******.default - LastPlatformDir=C:\Program Files\Mozilla Firefox; LastAppDir=C:\Program Files\Mozilla Firefox\browser
• i6******.default-release - LastPlatformDir=C:\Program Files (x86)\Mozilla Firefox; LastAppDir=C:\Program Files (x86)\Mozilla Firefox\browser

What's the next step?

You should also see the LastVersion listed in compatibility.ini.

What Firefox version in what location last used the profile with your personal data ?
Is that the current release (78.0.1) or is that the older Firefox version ?

It sounds like your main installation and your main profile are tied together.

Removing the unwanted installation can be accomplished by deleting its program folder, but that will leave some debris in the Registry. On the other hand, running its uninstaller --

C:\Program Files (x86)\Mozilla Firefox\uninstall\helper.exe

-- might cause a further file mixup. I'm not sure whether that's a good idea.

What is most mysterious is why the unwanted installation even fired up at all. Perhaps a .html or .pdf file launched from Windows Explorer, or a link from an external application, opened in the unwanted Firefox instead of the main one??

So, for some reason the old Firefox 72.0.2 version got started and you kept using it and the version create a new dedicated default-release profile.

Like posted above, you need to find out why you started using this older 72 version and not the current 78 release with your personal data.

It sounds like your main installation and your main profile are tied together.

You mean the FF that I now have open and the profile I've always used are tied toegther? That would be good, correct?

What is most mysterious is why the unwanted installation even fired up at all. Perhaps a .html or .pdf file launched from Windows Explorer, or a link from an external application, opened in the unwanted Firefox instead of the main one??

It could be that when I uninstalled winpdfeditor.exe from the control panel, I clicked once too many times and hit that second FF (v72) in the apps list. The mystery version came to life right then.

So... what do I delete to get put of this? Do I trash both the i6******.default-release profile and C:\Program Files (x86)\Mozilla Firefox\Firefox.exe ?

Or would it be safer to do a Windows system restore to a point anytime before this morning?

Before I do anything though, can someone tell me: if a Firefox profile gets overwritten or deleted, can it be restored from a backup (i.e. copied and pasted back into the Profiles folder)?

So, for some reason the old Firefox 72.0.2 version got started and you kept using it and the version create a new dedicated default-release profile. Like posted above, you need to find out why you started using this older 72 version and not the current 78 release with your personal data.

See reply to jscher2000 about how it might have happened.

I think that best would be to uninstall the Firefox 72 version via the Windows Control Panel.

You can use the Firefox Profile Manager or the about:profiles page to remove the default-release profile and its files as this ensures that you remove the files in both "AppData\Roaming" and "AppData\Local" as listed on about:profiles.

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

Before I do anything though, can someone tell me: if a Firefox profile gets overwritten or deleted, can it be restored from a backup (i.e. copied and pasted back into the Profiles folder)?

That often works, certainly for core Firefox data, but users report that add-on data doesn't always come back (the files are there but not used for one reason or another).

Thanks for your advise, will let you know how it goes.

Used Firefox Profile Manager to delete the unwanted profile, but I'm letting sleeping dogs (FF 72) lie for now. Main thing is the only FF I have working is the one I want.

In conclusion, updating to FF 78 was not the cause. Most likely it was a freak accident in the Windows control panel. Thanks to both for the assistance.