The Duke o' Death is a unique, super-powerful car in Grand Theft Auto 5's single player mode that isn't meant to be found or driven in Grand Theft Auto Online. Some folks found an exploit, however, that allowed them to illegally import it like a Nissan Skyline. They are being dealt with. Hilariously.
Rather than just blacklisting the car and keeping it out of your GTA Online garage, Rockstar Games decided to just blow your ass up if you try anything funny. See for yourself in that video above.
Apparently, solving this exploit was easier to address with a server-side hotfix rather than a full patch. It's also a lot nicer than banning the cheaters, if being exploded to death is nice.