http://www.pcgamer.com/destiny-2-expansion-curse-of-osiris-appears-on-the-microsoft-store/

Either mistakenly or intentionally, the first expansion to Destiny 2—which won't even be out for the PC until October 24—has appeared on the Microsoft Store. Called Curse of Osiris, the expansion will feature "new story missions and adventures" set on the planet Mercury. 

"Journey through time and space to learn the secrets of Osiris, avert a dark future, and rebuild the ties between the legendary Warlock and his greatest student—Ikora Rey," the listing says. Players will explore the "mysterious 'Infinite Forest,'" earn new themed weapons, armor, and gear, and take part in new competitive activities and multiplayer arenas. Naturally, "and more" is also promised.