PC
A couple days before the release of the Oblivion remaster, my friend VISCERAL informed me that the video game streaming service Boosteroid mistakenly had the game visible in people's libraries. I was confident enough that I could get something out of this that I paid for a Boosteroid subscription, and a Mullvad subscription, as the build was spotted specifically on their Stockholm servers.
Through the information shown in the Steam client, We were able to determine the install size, and he posted about it on Twitter and received quite a bit of press coverage. I was unable to access the game files directly, but I discovered a method to exfiltrate files from the streaming service, and was able to pull the ID of the currently installed manifest.
Naturally, the first thing I did when it officially released was check the manifest against the released version to see if it was any different to the public version. For a brief second I thought it wasn't any different because the retail manifest just so happens to share the same first 2 digits. However, the build was indeed different. The build is from April 9th, and thus has no meaningful content differences, and it is a Shipping build, so it lacks any debug features not already present in the retail release. However, it does include the .pdb. The .exe and .pdb are the only files included for download here, if you for whatever reason really want the full build, the command to download it through Steam would be download_depot 2623190 2623191 8517267727986765939, though I cannot guarantee this will work.