If you have good news, you make your message as clear as possible. Do the same thing with bad news, for the sake of your readers.
When you book a flight with Air New Zealand, they send you an email. You only need to read the first line to know what’s up.
Then, when Air New Zealand are about to fly you somewhere, and they have a few things they think you might like to know about the flight, and what to do while you’re away, they send you an email. You only need to read the first line to know what it’s about.
But when Air New Zealand hear that their name is being used by criminal bastards trying to fool people into giving up their credit card details, the email is a little bit different.
I’d argue that the third message is the most important one, but because it’s bad news the headline is weak and empty.
If you’ve decided to publish a message, the rules of useful headings and being succinct don’t change, whether it’s good news or bad. No-one wants to be the messenger in a situation like this one, but put your readers before your apprehension and be straight up. It makes things easier and quicker to read, and shows your audience that you’re a strong communicator, even on a bad day.