A trapdoor is a concealed opening in a floor, ceiling, or wall that allows access to a hidden space. Often used in buildings, trapdoors can lead to attics, basements, or secret rooms. They are typically covered with a panel that blends in with the surrounding area, making them difficult to detect. In computer science, a trapdoor refers to a hidden feature in software or a system that allows unauthorized access. This can be a security vulnerability intentionally placed by developers or malicious actors. Trapdoors can compromise the integrity of systems, making them a significant concern in cybersecurity.