"Halo 5: Guardians" beta, which ran from Dec. 29, 2014 to Jan. 18, 2015, was put away — for good. But for some reasons, those who still have clients on their Xbox One console received a mysterious update, leaking the upcoming soundtrack of the game and a few screenshots from its multiplayer mode.

The beta version isn't playable anymore, but it got updated. Someone captured the update, according to Polygon, and uploaded the soundtrack on YouTube om Saturday.

So now, whoever took part on the beta test and still has the client in their consoles has an instant access to that leaked music.

Meanwhile, NeoGAF users posted screenshots of the multiplayer menus, where it showed option for customization and other details.

The same game website, Polygon, got in touch with a Microsoft rep and asked if the leaked materials will be a part of "Halo 5: Guardians" or if it's for something else. Unfortunately, the leaks were confirmed to be legit.

"It's unfortunate when work-in-progress content leaks, but this Halo 5: Guardians content is part of our ongoing private, external testing for multiplayer," the rep said.

"We will continue to rigorously test Halo 5: Guardians to ensure the best possible experience for fans at launch," the rep added.

The game's soundtrack was composed by Kazuma Jinnouchi, the same composer who worked on "Metal Gear Solid 4: The Guns Of The Patriots," Geek Snack reported.

Meanwhile, the extent of the customization that was leaked showed weapon skins and other details for multiplayer mode, Warzone, International Business Times learned.

The new "Halo 5: Guardians" mode was designed to mix the player versus player and player versus environment elements, as per Softpedia. In addition, gamers can play cooperatively with the entire campaign.

"Halo 5: Guardians" is set to be released on Oct. 27, almost a year after the original multiplayer for the game was released.

The game can be exclusively played in Xbox One.