Just after the final release of iOS 10.3.2, Apple silently allows iOS 10.3.3 beta 1 for developer tester for iPhone, iPad. iOS 10.3.3 beta 1 comes with minor bug fixes and security updates.
Along with iOS 10.3.3 beta 1st, Apple also seeded 1st beta of macOS Sierra 10.12.6, watchOS 3.2.3, and tvOS 10.2.2 containing bug fixes and improvements.
How to download iOS 10.3.3 Developer beta 1 on iPhone
iOS 10.3.3 Developer Beta 1 is available for download to registered developer’s via OTA over-the-air on iPhone 7- 7 Plus and other compatible devices like iPhone 6s-Plus, iPhone 6 – Plus-,iPhone 5S-SE from iOS settings app running previous beta or you can also download iOS 10.3.3 Beta 1 through Apple’s online developer center and Apple Beta Software Program.
In case of mac, macOS Sierra 10.12.6 beta 1 can be installed through Mac App Store’s Updates tab.
For Apple TV, tvOS 10.2.2 beta 1 can be installed in Settings → System → Software Updates → Update Software.
And for Apple Watch, watchOS 3.2.3 beta 1 can be installed with the Watch app on your iPhone by tapping My Watch → General → Software Update.