http://www.macworld.co.uk/how-to/iphone/why-is-my-iphone-asking-if-it-can-update-carrier-settings-3597048/
http://support.apple.com/en-us/HT201270
its always safe with apple stuff. If there is a bug in an update, it will be fixed. You never have to worry about viruses or malware on iOS
Tell the to the masses of people who's iphones now have bad reception due to the 18.1 update. myself included.
