An elevation of privilege vulnerability exists when the Windows AppX Deployment Extensions improperly performs privilege management, resulting in access to system files.To exploit this vulnerability, an authenticated attacker would need to run a specially crafted application to elevate privileges.The security update addresses the vulnerability by correcting how AppX Deployment Extensions manages privileges., aka 'Windows AppX Deployment Extensions Elevation of Privilege Vulnerability'.
https://www.zerodayinitiative.com/advisories/ZDI-19-979/
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1385