Apple has released iOS 10.0.2 to address some early bugs. You can download the 88.2 MB update in Settings > General > Software Update or via iTunes. If you’re running iOS 10, you should install this update right away.
The big news with iOS 10.0.2 is a fix for a bug affecting iPhone 7 owners who were seeing Lightning-connected headphone controls stop working after a few minutes.
iOS 10.0.2 also resolves a bug that could cause Photos to quit for some users when turning on iCloud Photo Library and another that kept some app extensions from working.
iOS 10.0.2 comes hard on the heels of 10.0.1, which only those buying the new iPhone 7 or 7 Plus needed to download explicitly, since 10.0.1 was the first public release of iOS 10 for older devices. Most important in the iOS 10.0.1 update were fixes for issues that could affect Bluetooth connectivity and pairing with an Apple Watch; Adam Engst couldn’t pair a new Apple Watch Series 2 to his iPhone 7 until he upgraded to iOS 10.0.1. That update also fixed a bug that prevented the iPhone from recognizing “Hey, Siri” requests, addressed problems with audio quality for calls made over VoLTE, and improved the stability of the Camera and Contacts apps.
Regarding security, iOS 10.0.2 offers nothing beyond what was in iOS 10.0.1. The only security fix listed for iOS 10.0.1 is related to the remote jailbreak vulnerability discovered by Citizen Lab and Lookout — see “iOS 9.3.5 Blocks Remote Jailbreak” (25 August 2016) for more on that.