i updated firefox and now all my passwords are gone

Yes this does seem to happen to some users.

Have you researched this forum, it isn't that uncommon, but of course no one can see what you have.

Try a search top right for [passwords gone]

i didnt go over all but only a few in forum and didnt help. i see in the profile folder "logins.json-1.corrupt" with size of 153KB from a few days ago. when i open to edit this file in notepad it seems to show many all NULL chars.

Yes it is not a readable file as such, it You can try and create a new Profile, then exit FX, then put that file in the new Profile, restart and see what happens.

Passwords can be exported to a csv which can be read

it didnt work. does firefox still use logins.json on latest version or is it obsolete?

i noticed there is also a file logins.db and there is data in it when i open it with sql, but i dont know much what can be extracted from it, and i guess it doesnt store the passwords or perhaps they are encrypted

what else do you suggest to recover the passwords? thanks

If Firefox starts up after an update without your bookmarks and other settings, check whether your data is available in a different profile:

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it. The About Profiles page will open. This page should list at least one profile and could list many.

The profile that Firefox is currently using will show:
This is the profile in use and it cannot be deleted.

Please do not delete anything here; don't use any Remove buttons.

Do you have another profile named default 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, click the Set as default profile button for that profile on the about:profiles page. Firefox will use it automatically at the next startup.

For more information see Recover user data missing after Firefox update or reinstall.

Note: If your bookmarks are not available in another Firefox profile, see Recover lost or missing Bookmarks for other solutions.