There was a 1-3 second power failure today that crashed my desktop computer but the UPS maintained power to the fiber modem and mesh router, so my internet connection to the house was maintained. I restarted the desktop and launched Firefox. It proceeded to open all the tabs which had been open which is good. BUT it was very troubling that my log-in to my Investment Brokerage account was maintained and it did not request a Log-in Account Name and Password. A 2nd web account also maintained its log-in; so this is not specific to my brokerage. I have Firefox set up to NEVER save passwords; I use a separate Password Manager set up NOT to autofill account names and passwords.

Was this because the the UPS maintained the internet connection (for the 1-2 minute restart) while Firefox crashed and did not EXIT? Is there any setting I can make to prevent this from happening?