In a single click you can now set all AWS Systems Manager Agents in your fleet to automatically update to the Agents’ latest version. AWS Systems Manager Agent (SSM Agent) is Amazon software that can be installed and configured on an Amazon EC2 instance, an on-premises server, or a virtual machine (VM) to enable AWS Systems Manager to securely connect to, configure, and manage these resources. With the new single-click setting, it is much easier to ensure that all of your SSM Agents automatically have the most recent updates and capabilities. See the Automate Updates to SSM Agent page to get started.
from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/11/use-single-click-setup-aws-systems-manager-agents-automatically-updated/