Microsoft Win32k in Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows an information disclosure vulnerability when it fails to properly handle objects in memory, aka "Win32k Information Disclosure Vulnerability".
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8666