How do I prevent a Flask site running on Windows IIS from accessing other folders?

Question

Flask

Raised a Flask website on Windows IIS via fastcgi.
Very satisfied with the performance (speed).
I decided to try to look through files, folders (and any and from any disks).
And it turned out to be quite possible.
I even climbed into the files of other sites raised on the same ASP server.
How can I disable this using Windows IIS?

Answer 1

And how do you "flip through files, folders"?
write an example!
Maybe I can do it too... :(