As soon as security updates for supported Pixel and Nexus devices are paid much attention to, it proves that no opponent is as diligent in keeping its promises as Google. Currently, not only we can access factory images or OTA zips for the April Security update, but we also can see separately Android 7.1.2 Nougat builds.
Soon after the security update comes onto the market, there are patches for 1 vulnerability marked critical, 6 marked high, and 5 marked as moderate severity from the partial security patch level up to 1st April. Whereas, the complete security patch level up to 5th April consists of all above patches along with patches for 8 critical, 26 high and 14 moderate severity vulnerabilities. Details about the whole vulnerabilities can be searched at Google’s April Security Bulletin.
Users who are manually flashing can also choose to discover the security patches for supported devices either on Android 7.1.1 or on the newly released Android 7.1.2 build. In general, the latest Android version is integrated with the latest security update. Nevertheless, if there is something against your favor, you should downgrade to a previous version and the security update is still secured.
It is curious that the Nexus 6 get no option of an older build for the fact that both Android 7.0 and the form of NBD92G and NBD92F builds include the April security patch. Normally, these monthly updates do not supply a change-log; however, a change-log for the Google Pixel and Pixel XL devices has been posted by a Google Community Manager.
Gradually, these updates will become prevalent among all users through OTA. If you feel it too long to wait, you can manually flash the OTA or the factory image which are ready to be downloaded at their respective hyperlinks. Lastly, you have to make sure of downloading the correct build for your device.