The email mentioned in the tweet is over a year old, with the response fixing the issue over a year old...the tweet in question is pointing out that their decisions relating to security are extremely questionable, not that this was the way they got in.

This is also what he said in the Q&A session:

> I think the attackers must have used the same approach as the FTP server was open & credentials were not strong enough. But it was a sophisticated attack as the binaries were signed.