This is a pretty good idea, but does have an issue with shared passwords. In most attacks, the data on that site is compromised and changing your password afte

This is a pretty good idea, but does have an issue with shared passwords. In most attacks, the data on that site is compromised and changing your password afterwards just prevents further exploitation by others. What some password manager do is monitor for shared passwords (i.e. using the same password on Site A and Site B). This prevents attackers from cracking the password hash offline and trying the username/email and password in a bunch of different sites.