Stolen?
Yes. China in general, and its aerospace industry in particular (though it has competition for the title), is notorious for corporate espionage/intellectual property theft.
I wouldn't be caught dead on any airplane crewed by their pilots nor designed and built by their industry. The horror stories I could tell...
There's a reason their "indigenous" ERJ/EBJ program (Harbin) was terminated
--and it had nothing to do with the jet itself.