According to Wired magazine, Apple issued, on 23 January 2017, a bevy of updates. Wired tells us
Apple details over a dozen vulnerabilities in all in the iOS 10.2.1 release, including 11 focused around WebKit, the browser engine behind Safari, the App Store, and lots of iOS apps. They also include two instances in which a malicious application could execute arbitrary code with kernel privileges, which is to say, it could take complete control of your device.
Our recommendation, is do not dilly dally in updating your devices. The updates, announce to the cyber criminal world, that the window of exploitation opportunity is closing. The criminals may be expected to double-down to exploit those users who continue to have open a known, and closed exploitable vulnerability.
You may go to this Apple link to find your device’s update and an explanation of the underlying code adjustments: Apple Security Update Page.