As far as I am concerned, there isn't... Publicly that is.
I've looked it up countless number of times over the years, I am sure there is a method out there. But it will never be leaked. Maybe it will? Maybe not. Highly doubtful.
Also if there was a method PUBLICLY and if it wasn't patched quickly, there would be so many legit GT's in the market right now.
There are no private nor public ones. I am the only one to even come close to getting it to happen @fear tried it. But it would take far too long and be pointless in the long run. Very easily patched anyway.