I recently found that my saved logins had disappeared. Not sure if this happened after a Firefox crash, Firefox update or Windows update. Unfortunately after reviewing the information on recovering the file I found that none of the methods worked for me. Also since I had no idea this had happened I had already done some password resets on web sites and Firefox had saved them which most likely wiped out the backup logins file. This is a real black mark for Firefox. If the logins.json file is corrupted you should display a prominent warning on startup so that users have a fair chance to recover before inadvertently wiping out the back up file. I do not use mobile devices (and you should NOT assume that everyone does) so there is no other device to recover the logins from. Fortunately I save some passwords in a password manager so not all is lost. But its hard to have confidence in your browser if this can happen without warning or notification. Very sloppy work.