    def __init__(self, hs):
        super().__init__(hs)
        self.clock = hs.get_clock()
        self.client = hs.get_http_client()
        self.key_servers = self.config.key_servers
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.