alt Hacker News> Instead, the password managers each have their own finicky app-to-app mechanism for transferring passkeys from one password manager to another. (I think all the password managers kinda like that lock in.)
It's a nice simplifying step to talk about password managers here, but in the majority of the cases this won't be handled by a password manager, but rather by the device operating system, and the device manufacturers really like that lock in.
They're also in an especially good position to abuse it, because they now know every service that you authenticate and the webauthn "attestation object" field lets them set up a side channel with those services such that they can sell additional information about you.
Some people will tell you that the attestation object is not used in the consumer passkey system, so there's no way for this abuse to occur, but since it's usually going to be the device manufacturer who controls the password-manager-like component here, and they're the ones who stand to profit most from this kind of abuse, I think we need stronger guarantees than "the spec says you shouldn't do this unless the user is your employee and you paid for their device".
Until they fix this, I'm sticking with my mess of TOTP authenticators and yubikeys.
All of the major operating systems and all of the major browsers are password managers. Apple, Google, Microsoft, and Mozilla are all password managers. They all have apps that let you access their password managers on other operating systems.
You're right that all of the major password managers like their lock in. The Credential Exchange Protocol is just barely good enough that OS vendors can say they "support" it, but tricky enough to find that ordinary users probably will never try it. (Not to mention that it doesn't even work yet on Windows or Android.)
As for attestation, the good news is that Apple always returns 0s for the attestation ID (because Apple, like you, opposes it as a side channel), and so any public site/app that insists on attestation would reject all Apple devices. This gives smaller password managers like Bitwarden sufficient cover to 0-out their attestation as well.