I'd abuse it myself and then stash all the items on random accounts. Then eventually I'd make a guide and sell it. Eventually it would be leaked I'm guessing and fixed... so I'd hold onto the items I duped until they were worth more (like now).
I would tell my real life friends about it, even if they don't play Runescape.
Why? Because if it was something like duping gp/items, more people = faster output, then we would sell the items and make a shit ton of $$.
id probs make a goldshop and after rsgp dropped a heap cause id be selling cheap e.g. 30c/mil id probs sell the guide and the guide itself would easily be worth 30 000 /40 000 bucks cause you could like make that in a couple of days using that
I'd tell my friend that I was doing it, but no way in hell I'd tell them how LOL.
Only for like $10K+
Cuz you could dupe phats in seconds for liekkkk $100000000000000000M irl