https://wccftech.com/surface-firmware-updates-are-live-for-surface-go-2-pro-7-and-more/

Microsoft has released September firmware updates for several Surface devices, including Surface Laptop Go, Book 3, Surface Pro 7, and Surface Go 2. These latest updates bring system performance improvements along with addressing critical security vulnerabilities.

For Surface Book 3, devices running Windows 10 May 2019 Update, version 1903, or greater, are getting the following firmware updates: