I decided that my forum activity should be bit more than trying to fight all the spam we've been getting recently so here it is.
Researcher Christopher Domas found hardware backdoor (as far as I understand unintentional one) in one of bit more obscure x86 CPUs, allowing privilege escalation.
Whitepapers/slides: https://www.blackhat.com/us-18/briefings/schedule/#god-mode-unlocked---hardware-backdoors-in-x86-cpus-10194
Video: https://www.youtube.com/watch?v=_eSAF_qT_FY
He also had interesting talk last year concerning finding undocumented x86 instructions:
https://www.youtube.com/watch?v=ajccZ7LdvoQ