Apple finds out big security holes in its operating system so get the latest iOS update now. Most iOS updates involve security fixes of varying severity. But the latest iOS 10.2.1 protects against a wide range of potentially devastating attacks.
Apple tries to fix vulnerability in all in the iOS 10.2.1 release, including fix for Auto Unlock, termination of contacts, securing access to kernel privileges, fix for WebKit against maliciously crafted web content, and fix to a problem with Wi-Fi.
When you have a good Wi-Fi connection, go to Settings > General > Software Update. Tap Download and Install.