Nice and to the point, makes it clear that this is early, explains the current scope, tells us to expect a follow up as the information makes its way to them. I like this tbh and I hope people won't punish them for not including more info when this is clearly in the early days of investigation.
It was only DETECTED on the 13th, and they suspect had been going on 'for some time'. And basically not sure if user data was touched but they suspect or haven't provided it yet buly saying'NOT'. I want answers.
You do not have the option of (C) Vendor should tell me about a breach they don't yet know about.