    def __init__(self, hs):
        self.hs = hs
        self.auth = hs.get_auth()
        self.client = hs.get_federation_http_client()
        self.clock = hs.get_clock()
        self.server_name = hs.hostname
        self.store = hs.get_datastore()
        self.max_upload_size = hs.config.max_upload_size
        self.max_image_pixels = hs.config.max_image_pixels

        self.primary_base_path = hs.config.media_store_path
        self.filepaths = MediaFilePaths(self.primary_base_path)

        self.dynamic_thumbnails = hs.config.dynamic_thumbnails
        self.thumbnail_requirements = hs.config.thumbnail_requirements

        self.remote_media_linearizer = Linearizer(name="media_remote")

        self.recently_accessed_remotes = set()
        self.recently_accessed_locals = set()

        self.federation_domain_whitelist = hs.config.federation_domain_whitelist

        # List of StorageProviders where we should search for media and
        # potentially upload to.
        storage_providers = []

        for clz, provider_config, wrapper_config in hs.config.media_storage_providers:
            backend = clz(hs, provider_config)
            provider = StorageProviderWrapper(
                backend,
                store_local=wrapper_config.store_local,
                store_remote=wrapper_config.store_remote,
                store_synchronous=wrapper_config.store_synchronous,
            )
            storage_providers.append(provider)

        self.media_storage = MediaStorage(
            self.hs, self.primary_base_path, self.filepaths, storage_providers
        )

        self.clock.looping_call(
            self._start_update_recently_accessed, UPDATE_RECENTLY_ACCESSED_TS
        )
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.