Following failed attempts to gain control of a well known Arab activist's iPhone, Apple have issued an update to iOS that EVERYONE should download and install as soon as possible. If you have an Apple device that is running iOS 9, you should install update 9.3.5 immediately.

According to Apple’s release notes that accompany all updates, iOS 9.3.4 is all about one (slightly vague) thing: “iOS 9.3.4 provides an important security update for your iPhone or iPad and is recommended for all users.”