It's no problem, as long as it's a one-time-only password and has a limited lifetime (ideally only a day or so). It's similar to a password reset URL, which is

It's no problem, as long as it's a one-time-only password and has a limited lifetime (ideally only a day or so). It's similar to a password reset URL, which is also a password equivalent, but only usable once. At least it's better than asking for your mother's maiden name.