As previously reported, there were accusations that US guild Exodus used an exploit to obtain the World First of the last unclaimed Hard Mode in Ulduar -- Alone in the Darkness. As it turns out, these accusations were true and blue poster Daelo posted on the official forums that the Yogg-Saron encounter was hotfixed on all servers to prevent this from happening in the future. Owing to this, Exodus' kill is no longer recognized by some achievement trackers.
Contrary to some reports, however, Exodus released a statement on their website that members of their guild were not banned, clarifying that Blizzard meted out a 72-hour suspension for their abuse of game mechanics. They argue that the encounter wasn't beatable to begin with, similar to the C'thun fight in Ahn'Qiraj before it was fixed, prompting the exploit. In the same statement, Exodus also points at Ensidia's arguably hypocritical stance of complaining about the abuse considering Ensidia used similar questionable methods to achieve other World Firsts. Serennia mentions this behavior in his column at wowriot, as well, bringing into question Blizzard's apparent double standard when meting out punishment.