The threat model described in TFA is that someone convinces your agent via prompt injection to exfiltrate secrets. The simple way to do this is to make an outbound network connection (posting with curl or something) but it’s absolutely possible to tell a model to exfiltrate in other ways. Including embedding the secret in a Unicode string that the code itself delivers to outside users when run. If we weren’t living in science fiction land I’d say “no way this works” but we (increasingly) do so of course it does.