How?
"The researcher, who goes by the pseudonym SandboxEscaper, says the bug is present in the code handling advanced local procedure calls (ALPCs)..."
In case anyone else is curious:
"Advanced Local Procedure Calls (ALPCs) An advanced local procedure call (ALPC) is an interprocess communication facility for high-speed message passing. It is not directly available through the Windows API; it is an internal mechanism available only to Windows operating system components."
Apparently Windows 10's internal communications channels aren't as internal or private as they hoped. Kind of ironic isn't it?
Biting the hand that feeds IT
