The reason I ask is mostly due to how Google Chrome installation works once you click the "Accept and install" button from Firefox. After you click the installation is started directly and when it's completed Chrome itself starts up.

Firefox does not show any "Save" or "Confirm" dialogs after you click the Install button (on Chrome install web page).

Now, is this standard behaviour? Or might it be due to having an old version of Chrome already on the computer (Note: The new version was still installed from Firefox).

Seems a bit risky to me, all you have to do is fool the user to click something and then you can do whatever you want on his machine, or? Personally I thought things like this only worked with IE/ActiveX.