If we make it strict enough to block exfiltration, it'll block the external libraries from loading. So that means we have to load our scripts from the same origin instead of external origins (as jclarkcom suggested).
But the whole reason for CSP was to allow us to use external libraries without exfiltration risk. If we stop using external libraries, then our motivation for using CSP is gone. So CSP is useless for the purpose of this conversation.
