There are reports all over the web about the KB3093266 update failing. I have this issue too. Numerous “fixes” have been posted and not a single one of them works for everyone. Some folks are manually downloading this update from non-official sources. I advise against it. Relax folks, it ain’t that important. Microsoft will fix it.
Solution
RunAs Administrator the following command
sfc /scannow
This worked in normal online mode, ran sfc /scannow with admin rights, rebooted windows. The udpdate installed successfully after the reboot. If there are issues running it in the online mode it might be better in offline mode.
Other Things that have been mentioned or could be tried:

answers.microsoft.com/en-us/windows/forum/windows_10-update/...
Window 10 update failure. I keep getting the following error when I try to update Window 10?
(KB3093266) - Error 0x80004005
All my updates has failed.

news.softpedia.com/news/windows-10-cumulative-update-kb30932...
KB3093266 is the latest cumulative update for Windows 10 provided by Microsoft, but just like the previous versions, this one is experiencing some installation issues that prevent users from getting it up and running on their computers.
Manuall ...

tweakhound.com/2015/10/01/windows-10-cumulative-update-kb309...
There are reports all over the web about the KB3093266 update failing. I have this issue too. Numerous “fixes” have been posted and not a single one of them works for everyone. Some folks are manually downloading this update from non-offici ...

www.tenforums.com/windows-updates-activation/24638-windows10...
I received a Windows 10 Update #kb3093266 today, and it's now waiting for me to re-start the P.C. to complete the installation.
The problem is that I only see one reference to this update on the internet, and it's in Japanese. As usual with Win ...