Microsoft is rolling out the first batch of September optional updates for Windows 10. The optional update is available for version 1909/1903 and it includes general bug fixes and non-security improvements. Microsoft also noted that optional update won’t download or install automatically on your device unless you manually select ‘Download and install’ in Windows Update page. The update will enable a new notification in Internet Explorer 11 to inform users about the end of support for Adobe Flash in December 2020. It also reduces distortions and aberrations in Windows Mixed Reality head-mounted displays (HMD)
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-optional-update-kb4577062-v1909-1903-released/