We don't have any official change-log of this update but we do have the APK file to download. So for the timing we have installed it to find out the full change-log of this update. Below is the first new thing which we found in today's update.
It seem like there is the security update have been pushed by the Google today.
You can download today's update from the below link:
Google Play Store v8.1.27 APK