remnant8243
In the strictest sense, having apps installed is a risk, even if you do not use them. A scenario is imaginable, involving a malciouse app, some exploit that is using ipc and the installed app.
(if it is not disabled) (maybe there are other attack surface too, it defenitly does increass the attack surface)
Not sure if this specific exploit type is happening in practice at all, and you do not need to worry about it.
For firefox the warning is only about the app itself as mentioned before.
(It is about using the browser, it is easier for webcode to exploit geko then vanadium^^)
edit: a more likely scenario would be an app (that you do not use) and a link, you click on 'open in app' by accident, and it might result in who knows what^^