If you're seeing this security update reminder on some of our Macs that previously had another MDM, which has been removed.
The reason you are seeing this screen is that a service in the background of your device is still running on your device. You can check the location below to check this.
/Library/LaunchAgents/com.xxx.updateupgrade.plist
/Library/LaunchDaemons/com.xxx.updateupgrade.plist
This service periodically checks "/Applications/Utilities/Nudge.app" against the JSON at "https://eam-nudge.s3.amazonaws.com/default.json". To stop this service, you can follow the steps below;
sudo launchctl unload /Library/LaunchAgents/com.xxx.updateupgrade.plist
sudo launchctl unload /Library/LaunchDaemons/com.xxx.updateupgrade.logger.plist
You can then delete the configuration file of this service.
sudo rm /Library/LaunchAgents/com.xxx.updateupgrade.plist
sudo rm /Library/LaunchDaemons/com.xxx.updateupgrade.logger.plist