It's not that hard to set up cold wallets and multisig setup to prevent this from happening, this will add some complexity and it could slow down things, but security would be much better.
I wonder if this could be revenge of someone who got their money seized on Fixedfloat, or something bigger is behind this attack...
This is the message I see on their website:
Technical work is underway, we will be back soon!😇
If you need to contact us, you can do this via chat.
Lot of people are pissed in twitter: