Today seems to be the day everyone is pushing out updates, and Nvidia is another company doing exactly that with both of their Shield tablets (the original and the K1) getting new OS updates today. This update for both tablet addresses some security issues, as well as adding Vulkan conformity to each one.
For the original Shield tablet, this update will come in as version 4.4, while the K1 will have this update chalked up as version 1.5. The update is identical for both tablets, so instead of just repeating everything for each device, everything that is talked about is applied to both tablets.
Nvidia Shield and Shield K1 Tablet changelogs:
The best part of this update is the boot loop fix, which a number of people have been dealing with including one of our own writers here. So if you have a Shield Tablet or a Shield K1 Tablet, keep an eye out for the update to arrive. You can also try to manually grab it without waiting for the notification to show up by heading into Settings -> About -> System Updates.