The main downside is that setup requires an active Internet connection, and that the latest version of Firefox is downloaded and installed. In other words, users will get the latest version of Firefox when they run the installer and they may re-use it. Unlike the offline installer, which always installs the version of Firefox that you downloaded, stub installers query Mozilla during installation so that the latest version of Firefox is downloaded and installed. The stub installer has advantages and disadvantages over full or offline Firefox installers.

All you get when you hit the 'download now' button on the Mozilla website to download a copy of the Firefox web browser is a so-called stub or net installer.