What about the rest of your profile? Settings, bookmarks, history, passwords . . . .

Firefox 80+ has a logins-backup.json file in the profile folder that can be used in case of issues with logins.json or to undo an accidental delete of a login, so you can check if you can find this file in the profile folder or in a backup and replace the current logins.json. Make sure to keep a backup copy of all involved files (logins.json and key4.db and logins-backup.json)

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

Help -> More Troubleshooting Information -> Profile Folder/Directory: Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

If you use a Primary Password then you can prevent losing passwords by canceling the PP prompt. You need to logout beforehand by canceling a PP prompt, e.g. by clicking the eye icon in Lockwise (about:logins).

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

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.

Hallo! Tanks for your answer. Rest of user data bookmarks, history remains. Only all of saved login data has disapeared. Fortunatny I have it on other computer. Im gonna off-line save it to file to avoid deleting it by syncronisation

Anyway - I like to know what happened. its lokks like kind of Third party activity. How to find out time location it was deleted?

There are so many possibilities, it would be hard to tell.

So, were you able to restore your passwords? If so, That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.

I lost all save password, bookmark all the data. how to recover?

See:

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