@alvarosanchez I'm interested in the switch-user functionality, as discussed in alvarosanchez/grails-spring-security-rest#125. However I unfortunately need it now :-D More seriously, could you give me some precise pointers to do the simplest switch user functionality possible ? I don't need to be able to switch back, I don't even need to know that the current user has been switched to. All I need is for an admin user to be (re)authenticated as a given other user with its username via a POST. From what you describe as what would be necessary to implement the switch-user-spring-security-like functionality, I guess the authentication as another user is not the most complex part; but I have no idea where to begin with. Thanks a lot and sorry..