Looks like there are some Halo: Infinite spoilers out in the wild.
The first technical test for Halo: Infinite multiplayer is live for Halo Insiders, and along with being able to play against bots, something else was included in the test – something 343 Industries didn’t mean to include.
That something is files related to the game’s campaign. But, of course, the files have been leaked online by data miners along with other information inadvertently included in the tech preview (thanks, Neowin).
According to the game’s project lead Joseph Staten, these files were included in the tech preview by accident.