Okay, so I'm not the best bug explorer of all time, you can be sure about it :D
Basically, I was trying to reach the very top of the Ironforge bank building (unreachable otherwise). The trick involves a multi-passengers mount (or a fear/blink) - you can actually cross the mountain wall.
Then you jump and safely land on the Bank :-)
...but I kinda missed and... fell in the lava :D
Luckily I got WTFRESCUED by my mate!