So, what is that afterall?
https://www.minibb.com/forums/manual.html#upgradesNot an upgrading script (because, you know, it would take us 2x more time to write this script else miniBB itself), but a point to an algorithm, which could make your upgrade painless.
Automatic upgrade script will actually mean your forums folder is opened for everybody to update the files. And it means, it is
highly vulnerable. We're trying to implement the secure script. If you like to be lazy and do not understand, what does it mean to upgrade the software, following all instructions - then sorry... miniBB is not your choice.