A method, system and computer-usable medium are disclosed for validating user credentials submitted to a data source by an untrusted intermediary. An untrusted intermediary attempts to access a data source on behalf of a user. The untrusted intermediary challenges the user to provide credentials of the type and format required to access the data provided by the data source. The user's trust client connects to an authentication service and identification credentials of the required type and format are generated. The identification credentials are conveyed to the user's trust client, which then provides them to the user's client, which in turn conveys them to the untrusted intermediary. The untrusted intermediary then presents the identification credentials to an authentication plug-in of the data source. The authentication plug-in validates the authenticity of the provided credentials with their associated authentication service. Once the credentials are successfully validated, the requested data is provided to the user's client by the untrusted intermediary.