My guess is that Firefox accidentally created a new profile for you and set that as the default. We've seen that issue recently because Firefox recently changed how it handles profiles.

Usually, fixing this is pretty easy. Just type about:profiles in the Firefox address bar. This will load a list of profiles on your computer. Press Launch profile in new browser on whatever profile is not in use. If it has the data you are looking for in it, just select Set as default.

There have also been some cases of Firefox using a separate profile when you use it to open a link from another program (for example, if you click a link in the Thunderbird email program). In this case, it's the same steps.

Hope this helps.

What security software do you have?

There have been reports that AVG/Avast is causing issues with passwords disappearing. You can check the profile folder to see if there are logins.json.corrupt files present. If you find such a file then try to rename logins.json.corrupt to logins.json.

• keep a backup copy of all logins.json files

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

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Thanks for your easy to understand note, Wesley. I did what you said, but it didn't fix the problem. Seems I only have the one profile. Thank you though.

Wesley Branton said

My guess is that Firefox accidentally created a new profile for you and set that as the default. We've seen that issue recently because Firefox recently changed how it handles profiles. Usually, fixing this is pretty easy. Just type about:profiles in the Firefox address bar. This will load a list of profiles on your computer. Press Launch profile in new browser on whatever profile is not in use. If it has the data you are looking for in it, just select Set as default. There have also been some cases of Firefox using a separate profile when you use it to open a link from another program (for example, if you click a link in the Thunderbird email program). In this case, it's the same steps. Hope this helps.

For more info on cor-el's answer, check out this recent article: https://www.ghacks.net/2019/06/14/if-you-lost-all-passwords-in-firefox-read-this/

If renaming the logins.json.corrupt back to logins.json works then I don't think that the file is actually corrupted, but that Firefox isn't able to open the file properly and thus wants to start with a fresh file and renames the old file. This would suggest that AVG locks the file for write permission or at least prevents Firefox setting (exclusive) sharing permissions properly. I don't know if there are tool that can verify this and this might only happen during startup (i.e. AVG may think that it needs to scan each file that Firefox opens).

I found the bug report mentioned in the Ghacks article and read it and it appears that I am right about this. See comment 24.

• Bug 1558765 - Saved logins and passwords missing after update to 67.0.2 - Problem in AVG

the issue did not affect Avast users, only AVG users that have purchased the standalone "AVG Password Protection" product.

AVG does not modify the file nor does it delete it. It only prevents Firefox from reading from it. From our understanding, FF renames the logins.json file to logins.json.corrupt upon subsequent retries to logins.json-1.corrupt, logins.json-2.corrupt and so on. I am not sure right now if there is any mechanism to recover these passwords back from inside FF. Renaming this file (copy) back to logins.json restores Firefox ability to read it again.

Thank you everyone. Cor-el, the article exaplaind it and I was able to find the file and rename it - all back now. Phew and thanks. :)

See also:

• https://support.mozilla.org/en-US/kb/passwords-disappearing-avg-security-software