Xcode 8 includes Swift 3, and SDKs for iOS 10, watchOS 3, tvOS 10, and macOS Sierra.
About the security content of Xcode 7.3.1
This document describes the security content of Xcode 7.3.1. For the protection of our customers, Apple does not disclose, discuss, or confirm security issues until a full investigation has occurred and any necessary patches or releases are available. To learn more about Apple Product Security, see the Apple Product Security website. For information about the Apple Product Security PGP Key, see How to use the Apple Product Security PGP Key. Where possible, CVE IDs are used to reference the vulnerabilities for further information. To learn about other security updates, see Apple security updates.