THis is most likely a bug that connects the ppl in the same world together (like azria has a world number and each tower room has a seperat number) When this occurs u are completly connected.. lets say ur char is a Blade and there is a Jester in the same world as u. if the Jester uses critical swing ur char will allso recive this buff and the jester will recive any self buff u use..
simply wait for the server to restart and everything should be fine and back to normal