Which REST security principle requires validating access to every resource and not relying on cached permissions?

Complete mediation is a security principle that mandates every access to every object must be checked for authorization. This ensures that even if permissions were previously granted, they are re-validated for each subsequent request, preventing unauthorized access if permissions change or are revoked. It directly addresses the risk of relying on stale or cached permissions. Economy of mechanism advocates for simple, small security mechanisms that are easier to analyze and verify. Separation of privilege requires multiple conditions to be met for access, enhancing security. Least common mechanism aims to minimize shared mechanisms to reduce potential attack surfaces. While all are valid security principles, only complete mediation specifically addresses the continuous validation of access for every resource.