I have a wild idea on how to get a chance to be alerted to your grandma/grandpa browser password storage being accessed by someone shady.
Imagine a web service, which at the first glance looks awfully like a legit financial institution (and has a “bank” substring in domain name for looking juicy in those Ctrl-F search results).
Imagine all it does is: if the credentials are “correct”, an email is being sent (to you) with all the details of the attempted login.
Not really a silver bullet, but getting such alert would be pretty clear indication of someone trying to get advantage over your not so computer-literate family member.
Perhaps something like this already exist?
Are there better ways to passively monitor other people data breaches?