A remote code execution vulnerability exists in the way that the Windows Graphics Device Interface (GDI) handles objects in the memory, aka 'GDI+ Remote Code Execution Vulnerability'.
https://www.tenable.com/blog/microsoft-s-july-2019-patch-tuesday-what-you-need-to-know
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1102