For the Surface RT, this August 2013 firmware updates the UEFI firmware to optimize the audio experience at low volumes and removes a perceived pulsing in audio volume for some content, as well as some system drivers to enhance stability and reliability. For the Surface Pro, it updates the UEFI and System Aggregator (SAM) firmware to enhance system stability. It also reduces power consumption, and improves touch latency of the Type Cover and Touch Cover’s touchpad.
For those running Windows 8.1 Preview, Microsoft has also released several patches (hat tip to Pureinfotech) as part of its regular Patch Tuesday exercise. One addresses a critical vulnerability in Internet Explorer, and another improves Adobe Flash Player video playback. There are also a couple that provide fixes for adaptive streaming and Digital Rights Management (DRM) playback features.