Posted by Reddit user ChronosHero, a seemingly accidental Xbox Store listing shows a Halloween-themed loot box (an exploding pumpkin), the game's reward for leveling up, and its primary microtransaction.
Another Reddit user, TowerNine also posted a video of the listing. Blizzard has not yet confirmed anything about the event.
There's still some skepticism about the image, based on a couple of small details -for one, the double space typo after "Halloween" in the title. The other is slightly more interesting - that skull design on the candy in the background.
It's a design we've seen associated with long-rumoured character, Sombra who, according to those following her associated ARG, isn't expected to be revealed for at least 10 days.
With an end date for the Halloween loot boxes listed as November 11, and the Summer Games running for almost a month, that would put her reveal at around halfway through the event, which is unlikely going on Overwatch's current cycle of one content update per month. However, game director Jeff Kaplan did recently tease that the game's next hero should "see the light of day sooner rather than later"
Here's the full listing description, according to Chronos Hero:
"Celebrate Halloween with some frightening treats for our heroes during a new event: Overwatch Halloween Terror!
"Trick out your collection by picking up Halloween Loot Boxes, available for a limited time*. Every Loot Box contains up to four cosmetic items, including at least one Halloween skin, spray, highlight intro, emote, victory pose, player icon, voice line, or credits that you can use to unlock other items. More than 100 Halloween items are waiting to be unwrapped!
"If your Halloween Loot Box contains an item that is already in your collection, you will instead receive coins.
"*Halloween Loot Boxes are available to purchase or earn in-game until 11/1/16 at 4pm PT."
If this does turn out to be true, it sounds as though the Event will take a familiar form to the Summer Games, with themed items only available for a limited time, and only available as Loot Box random drops - a move that was widely criticised previously.
Looking to the wider future of Overwatch, it looks as though at least two new heroes and up to four new modes are currently in development.