Assuming that the exploit really is unknown, what better security could they have done to prevent it, without severely impacting usability? Compromises will ha

Assuming that the exploit really is unknown, what better security could they have done to prevent it, without severely impacting usability? Compromises will happen sooner or later when running a large number of public facing services. With good policy, the breaches will be well contained, which seems to be the case here. What more can be expected out of a premier hosting company, let alone Hetzner which is very cheap budget provider?