windows update 3138612 what is it?

[#1]

https://support.microsoft.com/en-us/kb/3138612 am I being bind, nothing on that page tells me what it is for?  Double checking as the optional updates I got this morning are all for downgrading to win10, all got hidden just unsure about this Important file the updater has listed

[#2]

Hmm... using the "Hi speed scroll function" to get to the bottom of that extremely long list of files... I found this

Quote

Keywords:     kbsurveynew kbfix atdownload kbexpertiseadvanced KB3138612

Which..... may.... or may not.... give you some idea... however... you can always answer the question..
Was this page helpful.....    and answer NO... then put some suitable comment in the box... 
I wont put my comment on there, on here, cos it will get censored ! ! ! ... 

[#3]

KB3138612 'contains some improvements to Windows Update Client in Windows 7 SP1 and Windows Server 2008 R2 SP1' that replaces a patch distributed back in October 2015 and since it's offered for Server as well, it is unlikely to have W10-specific "threats" therein.
I installed it some days ago to no ill effect whatsoever on either of my Windows 7 systems but, I did notice that my Windows Update has speeded up slightly with regards to checking and downloading on both devices.
I also updated the IE11 cumulative security update which apparently has some 'internal patch' to display a W10 banner, but only works with KB3123862 installed.
KB3123862 isn't installed on any of my systems, which is very clearly a Win10 telemetry item, so don't see any new banners in IE11 after testing.
Primarily I use Firefox so, IE11 doesn't get used unless absolutely necessary on some websites.

[#4]

Just remembered, as I don't use IE11 unless absolutely necessary, when I'm not using/need it,
I have my 3rd party firewall/ internet security suite configured to block IE11 connections to the internet that does not affect Windows Update in any way.