Are you speaking about scenarios that could happen ? or there is an actual threat going on, because I don't understand why It became suddenly important to verify signature while we didn't see such a thread in the past.
Wondering too.
Cobra made an alert on bitcoin.org:
https://bitcoin.org/en/alert/2016-08-17-binary-safety but no one knows why he did it and what he means by it. So right now now the
assumption is that something nasty have been compromised, but there is no proof of any such compromise yet.
Nothing has been compromised, at least the post does not indicate that anything has been compromised. The post seems to imply that something might get compromised in the near future, possibly by a state sponsored actor.
Someone suggested in the self-moderated thread that this was something to potentially discredit the Chinese miners in the future if they were to start to support a HF for a larger block size. I have no reason to trust cobra, and several reasons to distrust him, and cannot rule the above out.