If anyone is interested in why this update / patch has come about, here is a statement from the Russian Intelligence Services accusing the US of spying via iPhones:
THE FSB OF RUSSIA REVEALED THE INTELLIGENCE ACTION OF THE AMERICAN INTELLIGENCE SERVICES USING APPLE MOBILE DEVICES
http://www.fsb.ru/fsb/press/message/single.htm%21id%3D10439739%40fsbMessage.html
And here is the original research by Kaspersky, a Russian anti-virus company:
Operation Triangulation: iOS devices targeted with previously unknown malware
Operation Triangulation: iOS devices targeted with previously unknown malware
And here is a good article by BBC journalist Joe Tidy on why this might all matter:
Why is it so rare to hear about Western cyber-attacks?
https://www.bbc.co.uk/news/technology-65977742
More detail on Russian state sponsored cyber threat groups here:
https://www.secureworks.com/research/threat-profiles?filter=item-russia
If you are still interested, this is an excellent book to read:
Dark Territory: The Secret History of Cyber War