This is a minor maintenance release in the 4MLinux STABLE channel. The release ships with the Linux kernel 4.4.63. Additionally, some popular programs (DropBox, FileZilla, Firefox, Java, LibreOffice, PeaZip) have been updated, too. 4MLinux 21.2 includes changes in WiFi configuration files to fix the problem with password-protected access points reported by some users.
You can update your 4MLinux by executing the "zk update" command in your terminal (fully automatic process).