question about a bundle. It is possible to hide content of files, just to avoid clients seeing javascript code or any other sensitive data. But then how your bundle script could access these hidden files when bundle is installed at the client's account?

There is a checkbox on the file record to hide them in the bundle. If you are using them with the standard

define([./customModule]), function(./customModule)

syntax then they will work fine. If you are trying to access them via like

N/file

and reading the contents, I believe you need to leave them unhidden.