Not sure whether you're referring to CPU microcode or the OS in the management engine.

Microcode is remarkably tiny and heavily encrypted. I've never heard of anyone dropping hints as to what's in it, so if that's permeable at all I get the impression you'd probably have to have some rather nice friends to learn about it.

Regarding ME security, here's some interesting info I found a while ago: https://news.ycombinator.com/item?id=13782508