On Wednesday Apple launched the fifth beta versions iOS 10.3.3 and macOS Sierra 10.12.6 for registered testers and members of the Apple Developer Program. The latest beta versions came after iOS 10.3.3 beta 4 and macOS Sierra 10.12.6 beta 4, which were released by the developers on June 22, 2017.
iOS 10.3.3 beta 5 (build number 14G5057a) is available through the software update mechanism in the Settings app on a supported iPhone, iPad or iPod touch with the appropriate configuration profile. MacOS Sierra 10.12.6 beta 5 (build number 16G23a) in the 'Mac Updates App Store' tab.
The configuration profiles required to register your devices in the developer-only beta can be downloaded through the developer portal Apple.
iOS 10.3.3 is a bug fix that improves the security and performance of your iPhone, iPad and iPod, as well as the upcoming macOS Sierra 10.12.6 update for your Mac. These are likely to be the last updates for iOS and macOS Sierra as Apple is focusing on iOS 11 and macOS High Sierra ahead of their launch this fall.