[tialaramex]

WebAuthn doesn't have "passwords" it does public key crypto. So phishingsite.example gets a public key signed response saying "Yup, burner wants to sign into phishingsite.example" and the whole point of cryptographic signatures is that nobody can make it say mybank.example instead of phishingsite.example without invalidating the signature. So it's useless for breaking into your bank account.

There's no UI. Even if you are 100% convinced this is really your bank, you desperately want to sign in, you keep tapping that button, trying again, it can't help the bad guys. There is no "Yes I'm really sure this is my bank" option that destroys your security.

[Bnshsysjab]

What’s to stop a password manager behaving in the same way?

[tialaramex]

Compatibility.

Password managers have to be compatible with the reality of how passwords are used/ abused by site owners. When my preferred electricity supplier was bought by Shell (as part of an exercise in greenwashing the huge fossil fuel company) they rebranded and all their URLs changed overnight. My passwords still worked - but on these new URLs. This looks _exactly_ like a phishing attack, except for the huge advertising spend on a cynical rebranding exercise.

If you sell a password manager that fails in this scenario you're getting customer feedback saying this product doesn't work, fix it. How can you fix it? Add an override, destroy the security value of the product.

But WebAuthn comes out of the box enforcing this rule that the FQDN can't change. When Shell buys the electricity company and says "All your sites need to change" if they used WebAuthn the developer says "I tried that and it breaks login for all customers". "Tell them to override it, put up a banner saying so". "There is no override"... "OK, put the old site back". Done. Users saved from security lapses caused by corporate rebranding.

The WebAuthn people put a bunch of effort into thinking about evil things that can go wrong and defending against them. Having a clean slate to start from helped enormously.

[burner589432]

So... Nothing apart from some convoluted anecdote?

If currently there's no password manager in existence that doesn't let you override the plaintext password extraction / override feature, there's nothing to stop one being made. You could probably hook it in with a system level service which cryptographically signs them, too.