OAuth 2.0 Mix-Up Mitigation

This specification defines an extension to The OAuth 2.0 Authorization Framework that enables the authorization server to dynamically provide the client using it with additional information about the current protocol interaction that can be validated by the client and that enables the client to dynamically provide the authorization server with additional information about the current protocol interaction that can be validated by the authorization server. This additional information can be used by the client and the authorization server to prevent classes of attacks in which the client might otherwise be tricked into using inconsistent sets of metadata from multiple authorization servers, including potentially using a token endpoint that does not belong to the same authorization server as the authorization endpoint used. Recent research publications refer to these as "IdP Mix-Up" and "Malicious Endpoint" attacks.