Microsoft is now rolling out a new firmware update for the month of August 2015 for two of its Surface tablets (Surface Pro 3 and Surface Pro 2) and only for those users running Windows 10.
The August firmware updates are meant to improve stability to the operating system and bring performance enhancements to graphics, but no major changes are included.
According to the Microsoft Surface update history page:
Surface Pro 3
The Surface Pro 3 gets an update for Intel’s HD Graphics Family driver update (v10.18.15.4256) improves graphics performance and stability on Windows 10.
Surface Pro 2
The second generation of the tablet also gets the HD Graphics Family driver update (v10.18.15.4256) improves graphics performance and stability on Windows 10.
Surface 3, Surface 2, Surface RT, and Surface Pro do not receive any new firmware update.
The firmware update is rolling out immediately, it will download and install automatically, but you can always go to Settings > Update & security > Windows Update to check for the firmware manually.
Source Microsoft (link 1), (link 2)