Earlier quoted context omitted.
That would truly be the best outcome possible -- that LastPass sent out "Someone just used your master password" emails incorrectly i.e. those were false positives.
They are saying it’s just a credential stuffing attack and being that my master passphrase is only used for LastPass I’m hoping that is all that is going on. Their statement does say “It’s important to note that, at this time, we do not have any indication that accounts were successfully accessed” but I would still like confirmation the emails were sent even on invalid attempts.
As far as I can tell, the "Someone just used your master password to try to log in to your account from a device or location we didn't recognize" email we all received was only sent when a correct password was used. Incorrect passwords did not trigger that email.
But yes, it would be great to learn that those emails were sent incorrectly i.e. it was a false positive (i.e. someone tried to login with a wrong password, but the email above was sent anyway). It's still not great that the wrong kind of email was sent, but that would be a low level bug.