An elevation of privilege vulnerability exists in the Windows Installer when the Windows Installer fails to properly sanitize input leading to an insecure library loading behavior. A locally authenticated attacker could run arbitrary code with elevated system privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. The security update addresses the vulnerability by correcting the input sanitization error to preclude unintended elevation.
https://www.tenable.com/blog/tenable-roundup-for-microsofts-june-2019-patch-tuesday
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0973
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2019-0973