Upcoming Xbox 360 exclusive Halo: Reach has been leaked, arriving on public filesharing sites almost a month ahead of its official release date.
Microsoft admitted that a "security exploit" had enabled hackers to obtain all 7 GB of the game's code from Xbox Live Marketplace, where it was hosted for reviewers.
The download had carried a mock pricetag of 99999 Microsoft points (approximately £860), but also required a specially-provided code issued to select reviewers. However, an anonymous party was able to bypass these security checks.
Following the leak, which swiftly spread to public BitTorrent sites, Microsoft issued the following statement: "We are aware of claims being made regarding a security exploit related to Halo: Reach and are aggressively investigating the matter. We have no further details to share at this time."
Developer Bungie offered more comment, primarily intended to discourage storyline spoilers (which have already appeared on fansites).
"Posting to Discuss, Request, or Link To information or campaign spoilers from illegitimately obtained sources - including illegitimately obtained copies of Halo: Reach - before the game is officially released will be considered a leak and will be treated as such," read a statement on the studio's official forum.
"The moderation team is doing their best, but if you want to stay 100 per cent spoiler free, our best advice is to 'go dark' by staying off all internet gaming forums until you have played through the game."
Whether Microsoft will continue to offer review code via download may now be in doubt. A spokesperson had previously told Joystiq that "While we are thrilled to be able to take advantage of the technology to provide media with a more accessible and convenient review experience, there are no plans to launch Halo: Reach to the public through Games on Demand."
Halo: Reach is due for public release on September 14.