A trapdoor is a hinged or removable panel in a floor, ceiling, or roof that provides access to a hidden space or area. Often used in buildings, trapdoors can lead to basements, attics, or secret rooms. They are commonly found in theaters, where they allow for special effects or quick scene changes. In the context of computer security, a trapdoor refers to a hidden method of bypassing normal authentication or encryption. This allows unauthorized access to a system or data, often without the knowledge of the user. Trapdoors can be intentionally created by developers or maliciously inserted by hackers, posing significant security risks.