The off-screen image below appears the show the beta's listing in the Xbox One marketplace and its size. Developer 343 Industries' three-week Halo 5: Guardians multiplayer beta will begin Dec. 29, despite the image's release date listing of either Dec. 4, 2014 or April 4, 2014 (depending on whether one assumes the month or the date comes first).
We've contacted Microsoft for comment and will update this article with more information as we receive it.
If the image is verified, it wouldn't be the first time a screenshot leaked from unreleased or unannounced products on the console. Just this year, purported screenshots found their way online from the HBO GO app, Just Cause 3 and Titanfall.
Update: GameSpot reports that a representative from Microsoft told the publication that the size is a placeholder.