A system and method including: receiving, from a client device, an authorization request originating from an authorization module of an application executing on the client device, where the authorization request includes an identifier identifying the client device; causing transmission, based on the identifier, of a verification message to the client device, where the verification message includes a verification code; receiving a confirmation of the verification code from the authorization module of the application executing on the client device; authenticating the application based on the receiving the confirmation of the verification code; determining that the client device identified by the identifier corresponds to a user account including secure user data associated with a user; and transmitting a unique token verifying that the application is authorized to sign into the user account, where: the unique token uniquely identifies the user account to the application, and the secure user data is not shared with the application.