If I remember correctly, upgrading is just a question of taking a newer version of the installer and running setup.. What I'd like to know is if it is necessary to install each upgrade sequentially, or if it's possible to skip some. Probably a stupid question, but it's better to ask than risk something.
You can skip upgrades and directly install the latest version. But I recommend to create backups of the /root/ispconfig and /home/admispconfig directories as well as an SQL dump of the ISPConfig database.
