1. A method for validating a user on an application server, comprising: receiving a request for access from an external user with an external user identity at an access point of an application on an application server, wherein an internal user identity is configured to provide access to resources at the application server for users with that internal user identity; authenticating the external user based at least on user credentials associated with the external user in response to the request for access; upon successful authentication, switching the identity of the external user to the internal user identity for the application by pushing internal user information on a user stack for the external user, so that the internal user identity governs access to resources at the application server for the external user, wherein switching the identity of the external user to the internal user identity includes adding internal user context information to the external user identity; upon the external user exiting the application server, popping the internal user information from the user stack, so that the external user is switched back to the external user identity; and providing, by the internal user identity, to the external user, a higher level of privilege in the application server, that is unavailable for the external user as the external user identity.