Downloads with blocked data should be deleted from disk after some time if they are not unblocked first. The expiration time may be the same for all downloads, or different based on the associated verdict. The deletion check could be done at shutdown, similarly to what is done for downloads that don't need to be persisted, or at startup when past downloads are deserialized. The latter has the advantage of not blocking shutdown. On the other hand, the former may be simpler to implement and would only block shutdown when there are blocked downloads to expire, which should be rare.