An unknown person has uploaded 32TB of Windows 10 internal builds, along with some of the operating system’s source code. The data was uploaded on BetaArchive, an Internet forum dedicated to archiving software beta builds so users and developers can track how a project evolved over time. This most recent leak includes private internal builds for Windows 10’s next version, codenamed Redstone 3, currently available only for Microsoft employees only. The leaked source code is part of Microsoft’s Shared Source Kit program, and most of it was already available online.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-source-code-internal-builds-allegedly-leak-online/