Just read the article. Can't the same exploits be made on almost all the sites ?
Maybe, but I would assume Hufflepuff should have also checked the other sites after PD fixed the problem completely and launched the same attack if it is feasible. Until now, I haven't heard of any comparably amazing win on the other sites.
If he is exploiting it on other sites, maybe he is now trying to be more subtile, so they don't notice and fix the flaw?
