// We have existing userSession even if it wasn't attached to authenticator. Could happen if SSO authentication was ignored (eg. prompt=login) and in some other cases.
                // We need to handle case when different user was used
                logger.debugf("No SSO login, but found existing userSession with ID '%s' after finished authentication.", userSession.getId());
                if (!authSession.getAuthenticatedUser().equals(userSession.getUser())) {
                    event.detail(Details.EXISTING_USER, userSession.getUser().getId());
                    event.error(Errors.DIFFERENT_USER_AUTHENTICATED);
                    throw new ErrorPageException(session, authSession, Response.Status.INTERNAL_SERVER_ERROR, Messages.DIFFERENT_USER_AUTHENTICATED, userSession.getUser().getUsername());
                }