Xiaomi Mi A1 starts getting December 2017 security patches along with performance improvements and bug fixes. The OTA (over-the-air) update has already been available for the device with build number N2G47H 7.12.7, and since the OTA update is rolling out in phases it will take a week or more to get the notification on your device. If you cannot wait for OTA, you can also download the firmware and install manually.
Based on the Android 7.1.2 Nougat, the N2G47H 7.12.7 update does not include any major features, except latest security patches (patch level December 1, 2017). The OTA update just weighs 153MB and will improve the stability of the system. Also, the update includes general bug fixes.
For your information, Xiaomi has already started Android 8.0 Oreo Beta testing for Mi A1 (read on to know how to participate) and it is promised that the device will get Android Oreo update before the end of the year 2017.
If you have not received the new software update yet (N2G47H 7.12.7), just go to Settings > About Phone > Software updates. If update available, it will start downloading the latest update automatically. However, note that your device should be running on firmware version N2G47H.7.11.18 to apply the update.
How to download and install OTA update on Mi A1 Manually
– Download N2G47H.7.12.7 OTA update with December 2017 security patches for Mi A1 (codenamed tissot) [here].
– Save the OTA update on your phone, boot into recovery mode, and select apply update from sd card.
– Choose the ROM zip file to flash it. Once done, your phone will reboot.
Note: For a successful installation, phone battery should be at least 50% charged. This process will not wipe your data, however back up all data before proceeding with the installation. (Source – MIUI)