This is an exploit, sure to be patched out soon.
(I have only tested this in the Hospital so far, but assume it works anywhere)
You can pick the floor safe, get XP, then hack a terminal (get XP), use the terminal to lock the safe, pick safe again (get XP), lock safe with termianl, pick safe (get XP) ..... ad infinitum.
Sure it's a (very) small XP boost, kind of like modding a cheap gun and then selling it. Do with it what you will.