Firefox doesn't seem to engage in such behavior; but as with all apps where I'm given the option I've only enabled manual updating. Safari doesn't either, but I can't find any way to manage updating.
I cannot verify if this is available in El Capitan but in High Sierra anything coming through the App Store, including Safari and MacOS can be at least partially controlled by going to System Preferences > App Store and disabling "Automatically check for updates".
