iOS 9.2.1 released. Security improvements and bug fixes, etc.

iOS 9.2.1 was released today.

This update includes security updates and bug fixes, including an issue that could prevent apps from completing installation when using an MDM server. For the security content of this update, please visit the following website: https://support.apple.com/kb/HT1222?viewlocale=ja_JP

The main focus seems to be security improvements and bug fixes.
Let's quickly update it.

More importantly, iOS 9.3 has already been announced, and I'm really curious about that...