Javascript inheritance in QT app

[zugzwang]

Using Windows XP-Firefox, I can log onto a password protected website, then load a separate (local) web-page containing a Javascript app, and then use that Javascript app to "explore" the password protected website. In effect, the local web-page inherits the authorization granted by the initial sign-in.

I'll soon be migrating to Linux-Firefox-Qt-C++. Can the above functionality be emulated with Linux-<some web browser>-Qt? For example, can a QT app be similarly imbedded in a Firefox web-page? Alternatively, can the QT app be (Javascript[?]) - launched from the web-page and still be inheriting the appropriate authorization?