It's a UD7, I dont know what really caused this but it's down to one of three things in my mind
1. When I first got it, I ran it on the stock cpu cooler and when playing around with different multipliers and voltages temps got a bit high and could have scorched the cpu, the socket does look like it's melted a bit.
2. Condensation due to phase cooling
3. The same problem that caused yours to burn
Voltages used
vcore 1.62
vdimm 1.76
vtt 1.14
level 2 LLC
Max clocks 5.28ghz
I have replaced the cpu with another and used it for a while on similar settings with no signs of burns on it