C'mon people!
It has to be from a massive backfire that lifted the rear of the car. Bad gas
I've only seen such antics from very lightweight front engine front wheel drive race cars. I would think that the Porsche with a large percentage of weight in the rear would be physically incapable of doing a 'stoppie'. As we do not have the whole picture (is there a crest of a small hill in the background that we're missing) it's tough to pass judgement.
Who knows where the pic was taken?