The per-account password limit refused every attempt once ten failures
had landed in fifteen minutes, counted before the password was checked.
Ten guesses from two addresses therefore locked a password-only account,
the app's password sign-in included, and repeating them kept it locked
for as long as anyone cared to.
A place the account has signed in from before is now neither counted nor
held back: a remembered browser, a phone presenting the device id a login
of this account was issued to, or an address a session or device login of
this account came from in the last thirty days. Anywhere else gets five
free failures a day and then a wait that doubles with each failure, from
thirty seconds to at most fifteen minutes, instead of a wall. The per-IP
limit is unchanged, and an unknown identifier is limited the same way on
its hash.
Under an SSO-only policy, a password sign-in to an account other than the
one a pending link names is now refused before the password is checked,
so that exception no longer tells right passwords from wrong ones.
The SSO callback bound a verified provider email to the local account with
the same address on the spot. The local address is not verified: anyone
could register with it, or type it into their profile, and the SSO user
then landed in an account the other person still held the password to.
The callback now links nothing. It records the link it would make in a
sealed, ten-minute, HttpOnly cookie and sends the browser to the sign-in
page, and the link is made only when that browser then signs in to that
same account with its password (and second factor) or passkey. Under an
SSO-only policy the password form opens for exactly that account. The
native sign-in answers oidc_link_required; the link is confirmed once on
the web.
Moving an account to a new email address now also needs a fresh proof: a
sign-in or second factor in the last five minutes, or the current password
sent alongside the change. Without it the address is left as it was and
reported in rejectedFields; the rest of the save still lands.
Marc-André Bombeck