Login to account on minecraft server hack?

When you log into a server, it requires you to do /register (password) (password) right? It asks for you to /login (password) whenever you log into the server. So if there's an admin or donor that has creative and such, is there a hack that I can bypass his password and hack the server? My friend got into the owner's account with a program (that he made himself I guess, but he won't tell me) and has a bunch of god stuff. Does the program bypass it and let you play without doing the second thing I mentioned earlier? Or does it give you a password and you punch it in.

Help me out folks!

-Samuraiii

There might be an exploit in the login plugin or your friend just ratted the owner

Noo he tricked the owner to download the forceOP plugin that lets you OP yourself..... or knew an OP's password and hacked into that and owner'd himself xD
But seriously you cant crack xAuth it will take decades.... only the server owner with all the files has access to it

This is Highly Improbable. Your best chance would be to guess, or to DDOS the server which causes some login plugins to fail upon restart, at least for me it does