Four things closed after an audit of the API, the skill and the team extension. The extension signs every post it sends with a secret you paste once in its options page (version 1.31.0), and the server can now refuse anything unsigned. The server no longer fetches a media URL that points at a private or local address, whoever sends it. An uploaded file is refused when its bytes do not match its extension. And a token can be created for an owner or an admin only by the owner, because a token carries every right of the person it belongs to.