https://www.gamespot.com/articles/destiny-2-curse-of-osiris-dlc-leaks-bungie-confirm/1100-6453216/

Update: Not that there was much reason to doubt an official store listing, but you can brush away any suspicions you had about Destiny 2: Curse of Osiris. Bungie has confirmed it is real, with marketing director Eric Osborne writing on Twitter, "Curse of Osiris is not a leak. It's real! :)" Unfortunately, we still don't have any more details, including a release date, but at least we know for sure what to expect from the game's first DLC drop. The original story follows.

Following a report suggesting that Destiny 2's first DLC takes players to Mercury, those details have now been corroborated by a listing on the Xbox Store. The first Destiny 2 DLC pack, called Curse of Osiris, will indeed take players to that planet for an Osiris-centric story.