If you own a Pixel 2 or Pixel 2 XL you should have received the over-the-air update notification for January 1st, 2018 Android security update. The Software brings along Security enhancements, Fixes for Meltdown and Spectre security flaws.
The update weighs in at around 51MB. Google’s instructions explain that for a successful installation, the battery in your phone should be at least 50% charged and your device should be connected to a Wi-Fi network or LTE.
If you haven't got the notification of this new software update yet, Just go to Settings - About Phone - Software updates, and It will automatically start downloading the latest update. The update will take around 10-15 minutes to get Installed on your device.