[Cyph0n]

The same thing can be said about game/software cracking scene groups. I believe they were (still are?) at the forefront of practical reverse engineering techniques.

An extension of that is the emulation scene, but that tends to be done in public for the most part.

[shittyadmin]

I'm not sure it qualifies as an "invention", but they definitely do some incredible work. They're able to pull off full API emulations for things like Steam, Origin and even emulate UWP to a degree that allows applications to be run outside of the traditional UWP system. Professional reversers often use tools developed by crackers - things like x64dbg, ImpRec, unpacking scripts, etc are indispensable.

If it weren't for this community I'd feel far less in control of my own computer.