    def setUp(self):
        self.mock_federation_resource = MockHttpResource()

        self.mock_http_client = Mock(spec=[])
        self.mock_http_client.put_json = DeferredMockCallable()

        hs = yield setup_test_homeserver(
            self.addCleanup, http_client=self.mock_http_client, keyring=Mock(),
        )

        self.filtering = hs.get_filtering()

        self.datastore = hs.get_datastore()
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.