Pepper X has not, to date, been declared the hottest pepper in the world. Pepper X is one of Ed Currie's creation, so is the Carolina Reaper. I think Ed kinda prematurely claimed it was hotter than Reapers, and who knows, perhaps one of them was. Ed said they were being tested in late 2017, but it seems they did not yet test higher, because there hasn't been a peep about it since. The Reaper is still, according to Guinness World Records, the worlds hottest pepper.

Cayenne Diane
Pepper Gal