Was Android update notification genuine?

Today (5 Feb 2017) I was in Google Chrome and a notification of an OS update took over my Galaxy S4 phone. I wanted to halt it as I hadn't done a backup for a few weeks. I couldn't get rid of it by just back stepping so I deleted Chrome data in App Manager. I did my backup, but then when I checked for available updates the display "The latest updates have already been installed" - so either

 1. some data has been put in my phone by this unfinished update procedure, fooling my phone to think the update was applied

or 2. the update announcement was from a dodgy source which might have done something nasty with my phone.

Any help with this pse?

My present Android version is 5.0.1 Not sure if there is a later one available for the S4