    def _consumer(self, auth):
        auth.process_response()
        errors = auth.get_errors()
        if not errors:
            if auth.is_authenticated:
                return True
            else:
                return False
        else:
            current_app.logger.error('Error processing %s' % (', '.join(errors)))
            return False
A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.