Unlike the previous update which focused on adding new features and bug fixes, the new update fixes a bug caused in the last update. It Fixes bug of missing icon of Download app in 4.5.11.
The OxygenOS 4.5.12 for OnePlus 5 costs 45MB. OnePlus recommends to download it via WiFi or LTE connection. You can also grab the Firmware file, in case you haven't received the OTA update.
The update is currently rolling out for the users under OpenBeta OS, and later on, all the features will be added to the stable build of the OS. Have you received the update? Let us know in the comments section below.