An OTA build for the upcoming Samsung Galaxy Note8 Oreo update has leaked on the internet. The update is specifically for the Verizon version of the Note8 in the US running on the Snapdragon processor. Due to this, even though it can be downloaded and installed, it's only really available for one version of the device (SM-M950U).
It's hard to say in what stage of development this update is in but it's unlikely to be the final build and likely one of the interim betas leading up to it that somehow got leaked. It runs on Android 8.0.0 along with Samsung Experience 9.0.
We don't have a lot of details but some of the reddit users have reported back saying it works fine on their device. The usual advisories and provisos apply while flashing a build you found on the internet to your phone so proceed with caution.