A couple of months ago, the Linux Mint devs discovered that many Linux Mint users don’t regularly update their installations, leaving them vulnerable to attacks, and others run older Linux Mint versions that reached end of life and are no longer receiving updates.
Due to this discovery, the Linux Mint team decided to improve the Update Manager utility (which lets you easily install updates on your Linux Mint system) to notify users who don’t apply updates regularly more often. After receiving some negative feedback from users who didn’t understand the changes Linux Mint wanted to implement in Update Manager to make users update their systems on a regular basis, devs decided to implement a new notification system for updates through a pop-up dialog (just like Ubuntu).