In theory any code could be written at any time that does something good or bad. Sure.
But in reality, the people who actually work on these standards within the FIDO alliance do not want a world where every website/service makes arbitrary decisions on which password managers are allowed. That would be a nightmare.
But in reality, the people who actually work on these standards within the FIDO alliance do not want a world where every website/service makes arbitrary decisions on which password managers are allowed. That would be a nightmare.