    def render_POST(self, request):
        """
        Register with the Identity Server
        """
        send_cors(request)

        args = get_args(request, ('matrix_server_name', 'access_token'))

        result = yield self.client.get_json(
            "matrix://%s/_matrix/federation/v1/openid/userinfo?access_token=%s" % (
                args['matrix_server_name'], urllib.parse.quote(args['access_token']),
            ),
            1024 * 5,
        )
        if 'sub' not in result:
            raise Exception("Invalid response from homeserver")

        user_id = result['sub']
        tok = yield issueToken(self.sydent, user_id)

        # XXX: `token` is correct for the spec, but we released with `access_token`
        # for a substantial amount of time. Serve both to make spec-compliant clients
        # happy.
        defer.returnValue({
            "access_token": tok,
            "token": tok,
        })
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.