What is the ruling or harm resulting from installing a mirror inside the bathroom behind the door?

The question is unclear. If placing a mirror causes harm, then it must be removed, based on the Prophet's (peace be upon him) saying: "There should be no harm nor reciprocal harm." If the question is about the ruling of placing a mirror inside the bathroom out of necessity, then there is no legal impediment. However, it is disliked to look at one's private parts without need.