    def make_homeserver(self, reactor, clock):

        presence_handler = Mock()
        presence_handler.set_state.return_value = defer.succeed(None)

        hs = self.setup_test_homeserver(
            "red",
            federation_http_client=None,
            federation_client=Mock(),
            presence_handler=presence_handler,
        )

        return hs
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.