Aside from the usual silliness (like 70 new emojis? like, we really need more useless emojis) both of these address recently found KRACK Wifi vulnerabilities.
So get (un)kracking...
Ars Technica: Apple releases macOS 10.13.1 and iOS 11.1 with a KRACK fix and new emoji
Edit: The macOS update could take about a half hour, despite saying 2 minutes, then blanking the screen for 5 minutes, then saying 36, then 17, then 26...
Just let it run until you get a proper login screen.
Apple's concept of installtion time estimates is like the Red Room in Twin Peaks.