A more robust idea might be a versioned filesystem. Somebody hacks your browser, it overrides your files - no matter, you just rollback to yesterday's version. Of course, that'd require more diskspace, but diskspace is getting cheaper and most of it is used for content that is completely static (like games or photos or videos - not edited much unless you're a professional working with it). Also probably would be a bit slower but I think it can be solved.

I think there are a number of implementations of such things, but none mainstream enough.