you can always search for your model # on sony's site, hit the drivers&software tab, expand the latest firmware. I bookmarked my TV to make the process easier: https://esupport.sony.com/US/p/model-home.pl?mdl=XBR55X810C&template_id=1&region_id=1&tab=download#/downloadTab

I did find this post on Sony's support pages:

Sony is planning to reduce input lag* in HDR video gaming for previously released 4K HDR televisions via a network software update in order to play HDR video games more comfortably. Sony is in the process of testing the SW update and is targeting to have this available for customers in North America the beginning part of November.

I wonder if that's what this update is...

Same here on a 700D, no post on the Sony support site.

Previous version was android 6.0.1 with the 9/20/16 firmware PKG6.0514.0001NAA (1.6.0.05.14.1.00).

After update, Android 6.0.1, PKG6.0612.0004NAA (1.6.0.06.12.1.00).

I just installed it on my XBR-65X750D. I've poked around and don't notice any difference in features or functionality. No mention of this update on Sony's page, either:

https://esupport.sony.com/US/p/model-home.pl?mdl=XBR65X750D&template_id=1&region_id=1&tab=download#/downloadTab