Microsoft released KB4514359 cumulative update for .NET Framework 4.8 and 3.5 versions for Windows 10 v1903 on Patch Tuesday 10 September 2019. This patch will help the OS protect against the vulnerability CVE-2019-1142.
You will get KB4514359 automatically if you are using automatic Windows update. Still not get then go to Settings -> Update & Security -> Windows update and click on Check for updates.
KB4514359 .NET Framework 4.8, 3.5 Windows 10 1903 Changelog
An elevation of privilege vulnerability is found when the .NET Framework common language runtime (CLR) lets file creation in arbitrary locations. An invader who successfully exploited this vulnerability could write files to folders that require higher privileges than what the invader already has.
To know details of the vulnerabilities, navigate to the following Common Vulnerabilities and Exposures (CVE) –
To install the Standalone package of this security update for .Net framework Sep 2019 navigate to – Microsoft Update catalog.
Source – Release note.