Authentication and authorization of a privilege-constrained application

Methods and systems are provided for managing access to a client account related (CAR) resource. When a privilege-constrained (PC) application requests access to an individual client account, a single use authorization (SUA) code is created that is associated with the individual client account. The SUA code is routed to, and returned from, the privilege-constrained (PC) application to authenticate the PC application. The PC application, once authenticated, receives a permitted action token that identifies a limited set of privileges that the PC application is authorized to perform in connection with the CAR resource. The PC application provides the permitted action token to an access service. The access service limits access, by the PC application, to the CAR resource based on the permitted action token.