Welcome to release 18.9.1 of SQL Server Management Studio (SSMS)! Full documentation for this release and previous releases is available here: SSMS documentation.
This update is available through Windows Server Update Services (WSUS). Release 18.9.1 is applicable to previous versions of SSMS 18.x only. This package will fully upgrade any previous 18.x version.
Release notes can be found here: SSMS Release Notes.