引狼入室 (yǐn láng rù shì): lit. to show the wolf into the house; fig. to introduce a potential source of trouble

引yǐn狼láng入rù室shì

lit. to show the wolf into the house; fig. to introduce a potential source of trouble

Showing the wolf into the house yourself. For the hire, the partner or the shortcut that brought the problem in through the front door.