Windows IoT Core is Microsoft’s go on embedded and IoT devices, and already runs in enterprise environments and commercial handheld products, as well as in cool DIY projects. Windows IoT Core shares much of Windows 10 kernel, but it cannot be identical, right? Right! It needs to be efficient resources-wise, it should forget irrelevant features, and it must surely add new IoT-oriented features. Moreover, it is set to be deployed on various boards and sets of hardware, so a low-level access for developers is better be provided, to make it dev-friendly.The following RCE method presented here shows how dev-friendly == hacker-friendly: Along with known remote interfaces (SSH, WEB...), Windows IoT Core exposes a less-known interface, used by HLK for driver/HW tests. We examined this service & protocol, and will release a tool called SirepRAT that exploits them for RCE as SYSTEM, requiring no auth. Full internals of this proprietary protocol will be presented, that show how it undeliberately exposes a remote command interface for attackers, including RAT abilities such as get/put files on arbitrary locations and obtaining system information. While other dev interfaces are password protected, this method shows a new way to control the device bypassing any authentication.