The article describes a straightforward phishing attack that works specifically against accounts that are _not_ protected by passkeys:

> Depending on which multi factor method the account uses, the victim sees a matching fake screen, whether a one time code prompt, an authenticator app number match, or an SMS page.

The only sense in which passkeys have anything to do with this at all is that the attackers used the word "passkey" in their emails. When a phishing campaign with the subject line "Your Mailbox is Full, Log In to Fix Now!" succeeds, that does not demonstrate an interesting vulnerability inherent to your mail server's mailbox size limits.

In this attack, it sounds like the key step was that the user entered their username and password, thinking they were preparing to enter a passkey. It wasn't the passkey system itself (which would prevent this attack), it was the transition from password → passkey system that was attacked.

In any case, if you can get the user on the phone and convince them to let you walk them through a bespoke auth flow, I doubt there is any auth mechanism that would stop this. This is why every auth system these days is constantly telling you "We'll never ask for X", because at that point, the game is over.

Isn’t that a bug in the Microsoft software, not the pass key specification?