It sounds like a refresh install and not an update. Were you signed into sync before the update? You could sign back in to get things back. Or you would have to dig for your backups on your old profile. I'll let someone else post the steps for that.

Hi cm30308, sorry to hear about this problem.

As the first step, could you do a normal shutdown and restart of Windows 10? That should release any locked files and ensure that any pending updates are completed.

Assuming the problem continues:

As Engage mentioned, Firefox will sometimes suggest that you could speed up Firefox by performing a Refresh. Does that sound familiar? A Refresh shouldn't lose passwords or bookmarks unless it failed to run to completion. You could check your desktop for an Old Firefox Data folder. Do you have that folder?

If so:

Poke around inside and see how recent the files are. They may be useful for recovery.

If not:

Could you check whether your stuff is available in a different profile, as follows:

Profile Manager Page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

Do you have another profile named default or default-release or default-longnumber listed on this page? If so, you can check whether it is the one you were using recently by clicking its Launch profile in new browser button.

If it isn't what you want, simply close that new window.

If it IS what you want, back on the about:profiles page, click the Set as default profile button for that profile so Firefox uses it automatically at the next startup.

Any progress so far?

See also:

• https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update