Due to an accidental misconfiguration on part of the Official Mortal Kombat web server, users were able to browse one of the subdomain's file directory freely. Inside of the directories there were lots of character intro voice over files. These new voice overs are the same ones used before a match begins in Mortal Kombat (2011). By looking at all the filenames he easily discovered all new unannounced characters and potential story line spoilers and additional game features not revealed yet. There was some really awesome new stage music too. The files all appear to be assets for part of an iPhone optimized website or app and are not supposed to be accessible to the public. The issue was resolved by WB Games a few hours after word spread across the community, and the files are thusly no longer available to listen to.
We feel that not everyone may want to hear the news since the reveals have come before schedule and without official confirmation, so for now we will be treating this leak as spoiler material. We would rather protect them from those who want to learn of characters and features as NetherRealm Studios and WB Games wants to officially unveil them. Also keep in mind, since this is just a few sound files, we can't be certain what role (if any) these items relate to anything official in any final product.
Spoiler for Possible Roster/Story Reveals and Game Modes:
There are fighting intro quote clips for the following characters: Ermac, Goro, Kabal, Noob Saibot, Quan Chi, Shang Tsung, Sindel, Smoke & Stryker. As well as a file with a human sounding Sektor saying "For The Lin Kuei!" Keep in mind this may or may not be an indication of the complete roster for Mortal Kombat (2011). There are characters we know that are in the game that were not present in the sound files.
There was also announcer voice files that indicate there is a possible return of the popular Test Your Might mode and maybe the first return of Brutalities since Mortal Kombat Trilogy introduced them almost 15 years ago.
Head on over to ShawnBronald's thread to read more on it. So we also urge you to keep all spoiler discussion in that thread so the rest of the community can be excited as things are revealed.
Updated 5:00pm: Did some cleanup and clarification of the article and all it's updates to make it a bit more coherent.