What is the ruling on students viewing medical samples outside official hours in exchange for a sum of money given to a worker without the administration's knowledge, given that no one is harmed?

If the laboratory administration does not permit entry, then it is not permissible for students to enter without their permission. Paying money to officials to allow entry is a forbidden bribe. Students must repent from this act and discuss the matter with the administration to convince them, or seek alternative laboratories.