It's actually normal, and I have it too. Instead of calling it a bug or broken, I think it's rather a feature so that you don't need to spent more seconds to type /login password again.
This should only happens when you logged in again from the same IP or device after not a long time, so no need to worry about being hacked by other person,
except the person have access to your device in your house at that time. If another person trying to use your account from other ip or device, they will need to login 100%, like
Mykkull
stated above.
So, I repeat, this is safe and only happens to you, unless someone can use your device too, so there's nothing to worry about it. I don't know if there's a way to turn it off or not, but I'll try to look on it. Hope this answer your worries, have a nice day/night!