OnePlus doesn't forget about their previous phones even after premiere of their new flagship phone named OnePlus 5T. Previous flagship devices, OnePlus 3 and OnePlus 3T recently received new update in Open Beta version, and now we know exactly what it changes because OnePlus presented its changelog.
New update delivers fresh UI for Do Not Disturb mode, reduced battery usage in standby mode, improvements for Smart Text Selection and some updates in general performance and security, because this update supply new Google security patch which was released for other devices in October. If you want to test Open Beta, you can join official program on OnePlus's website and test new version of system on your own device.