Apple releases iOS 9.2.1, this upgrade has bug fixes & security improvements.

Changes on iOS 9.2.1
• Bug Fixes.
• Fix for an issue that could prevent the completion of app installation when using an MDM server.
• Security Improvements.

The iOS update is available via OTA(OverTheAir) going into Settings > General > Software Update or using iTunes.

For more information about the security upgrades visit Apples website: