In 18.104.22.168/Iijoki & JollaC it seems that the browser does not really save login/password pairs, even when it is asked and user clicks 'Save'. When accessing the same (https) login page again, the same saving question pops up every time. And this is in standard, not private browsing mode.
Peculiarly, /home/nemo/.mozilla/mozembed does contain key3.db and logins.json, but the latter does not seem to be updated. signons.sqlite is also missing, but that's likely deprecated already.
logins.json only contains