Google today posted the January 2017 Security Bulletin for Android whilst also uploading the factory images and OTA files for its Pixel and Nexus devices. The latest build of Android 7.1.1 featuring the January security patch carries the build number NMF26U/V for the Pixels.
Like with previous months, the January security bulletin is divided into two patch levels to provide OEMs with the most flexibility in quickly rolling out updates to fix the security exploits.
The first patch dated 1-1-2017 is a partial security patch and contains fixes for a critical Mediaserver vulnerability, with the one dated 5th January 2017 being the complete security patch and featuring security patches for multiple critical vulnerabilities. You can find details about all the security vulnerabilities fixed in the latest security patch in the January security bulletin.
The OTA update for Google Pixel and Nexus devices is also being rolled out by Google, and it should land on your device within the next week or so. If you cannot wait for the OTA, you can always manually flash the update on your phone by using the factory images or the OTA zip file.