Well, Microsoft is probably not particularly happy that this happened, but it appears as though the Chinese (ZH-CN), 64-bit version of the Windows 8 Release Preview has leaked just days before it is supposed to be officially released. The download comes in at 3.34 GB and most likely is only in Chinese, with an English version yet to make a leaked appearance.
While we haven't received proper confirmation that this is an actual Release Preview build and not a fake, Canouna mentioned on Twitter that the size seems to be legit. Other people in a related thread on the WinUnleaked forums have pulled apart a partially downloaded ISO and found an installer that appears to be for the legitimate Release Preview (build 6.2.8400). Apparently this guy over at PCBeta has already installed the build and can also confirm it is indeed a legitimate leak.
While we obviously can't post direct links to it, if you follow one or two Windows 8 watchers (or head to the sources) you should be able to find out where it is being hosted, but that is of course if you're interested in playing around with the Chinese version...
Update: Canouna has proclaimed that this build is "100% legit" after checking setup.exe and product.ini, pretty much confirming (along with other reports) that the ISO does indeed contain the ZH-CN version of the Windows 8 Release Preview.