[usrusr]

> It is probably a sophisticated cyberattacker looking for credentials

It is probably the script of a sophisticated cyberattacker leveraging some vulnerability for looking for credentials of thousands of people at once. Yes, the burglar is a total non-threat by comparison (unless they happen to be working for your very personal enemy intelligence agency)

Good security practice would add a memorized element to the stored passwords as an informal second factor. Are there password managers that have good support for that when auto-filling and updating?