Have you heard of Genode? It's a capability based system. Not related to Forth or any other kind of "cool" programming language, but might be fun to explore all the same.
unless the user could be convinced to give suspicious capabilities to unknown programs downloaded from the internetUnfortunately I bet that people can be convinced to do that, and often. Scammers already convince people to download remote access tools to allow them to connect. Not really sure how to mitigate that; I don't want to limit what people can do with their computer like iOS and Android do.