As posted by Rosalie Marshall in her today’s article, secret F-35 military plane design materials have been stolen presumably by Chinese hackers (?):

The hackers copied data relating to the aircraft system design by exploiting network vulnerabilities in computer infrastructure belonging to contractors helping to build the new planes.

They gave no more detail on network vulnerabilities revealed by intruders except for the fact that only online computers could be attacked and so more important information (stored on offline machines) remained intact.