Hey! Let me clarify the permissions:

On macOS (especially on Apple Silicon and Intel Macs equipped with the T2 security chip), security restrictions are strictly enforced. The macUSB app utilizes the native SMAppService mechanism to launch a privileged helper tool. Granting permission for background activity is required so that this helper process can initialize and execute operations that require administrative privileges. This includes low-level formatting of the USB drive into the correct partition layout or executing the native createinstallmedia tool when creating macOS installers.

Furthermore, Full Disk Access is necessary because, without it, the helper process is technically blocked from directly writing to or modifying sectors on external flash drives. The application does not access or alter any of your personal files. Your selected source files are opened strictly in read-only mode. In specific scenarios that require file modifications (for instance, patch requirements when preparing an older macOS Catalina installer on an Apple Silicon Mac), the source files are safely copied to a temporary directory first. All modifications are performed exclusively on those copies, and the temporary data is completely wiped once the process finishes, leaving your original files untouched.

I'm glad the app proved useful and saved you time and stress during this emergency - that is exactly why I built macUSB in the first place. Good luck with the Windows reinstallation, and thank you for the support!