Every month, basically like clock-work, Google posts a new security update for the Nexus and Pixel line of devices. This OTA is actually given to their partners about a month in advance, to help them push out the updates to their own devices as soon as possible. Today, Google posted the security patch for March 2017, and it's now available for your flashing pleasure. Google has posted both the OTA's and the factory images for those that own supported Nexus or Pixel devices.
Speaking of supported devices, those include the Nexus 6, Nexus 9 (WiFi and LTE), Nexus 5X, Nexus 6P, Pixel C, Pixel and Pixel XL. All of these are remaining on Android 7.1.1 as well. The Pixel and Pixel XL are getting build NOF27B, while the Pixel C, Nexus 6P, Nexus 5X, Nexus 9 WiFi and LTE are all getting N4F26T and the Nexus 6 gets N6F26U. Be sure that you are flashing the right OTA onto your device, you will need to be stock Android 7.1.1 with the February patch installed to sideload this OTA successfully. Otherwise you can flash the factory image, or simply wait for the OTA to hit your device, which should happen in the next few days.
This month we have two security patches. There's the March 1st, and then March 5th. The March 1st security patch has a few critical vulnerabilities being fixed like a remote code execution in mediaserver, as well as one for OpenSSL and BoringSSL. But the bigger security patch is for March 5th, which has a bunch of critical vulnerabilities being patched. One of which is an elevation of privilege vulnerability in MediaTek components and another for the NVIDIA GPU driver. Now the MediaTek components one doesn't actually affect Nexus or Pixel devices, seeing as none of them run on a MediaTek processor, they all use Qualcomm's silicon. Speaking of Qualcomm, there is also a vulnerability in Qualcomm components, but Google does note that devices that have Android 7.0 Nougat or later and have all of their updates installed will not be vulnerable to that vulnerability. You can check out the full security bulletin at the link below.