Not all hacks are used to steal data. It's an authoritative website. If this hack is used to host a fake PHP fix stuffed with credential stealers then you have a problem.
Oh I absolutely agree they should take it offline until the fix is ready, I just mean that the NCSC itself is very much still operational even if their public website is temporarily offline. Like a computer with the monitor switched off.
> Not all hacks are used to steal data
Sometimes, they just want to send spam. Ages ago, someone got a hold of our company's webserver and all they used it for was sending a ridiculous volume of emails. Our ISP spotted the traffic spike and pulled our server off the network.