iOS 9.2 Security Upgrades
There are over two dozen security fixes in the iOS 9.2 update, including some that users will appreciate and some that they might not even know existed before the fix.
One fix prevents an app from accessing contacts after you told the system not to allow it. Another important fix prevents someone from using Siri to see notifications that shouldn't appear on the lock screen. There are fixes that prevent user interface spoofing that could be used to trick users.
Apple also packs in a number of upgrades that prevent malicious action or activity from links or arbitrary code. The end result is a more secure iPhone, but it may limit the chances of the iOS 9.2 jailbreak.