Well done Twitter - they worked out how web browser caches work. This is some BS against FireFox (painted as a FireFox issue when actually it's Twitter who've allowed said data to BE cached in the first place) OR it's part of the movie to allow a scenario of how data got out…
If a hacker has access to your computer, then you've more to worry about than your web browser's cache….
Anons regularly clear their web cache anyway, right anons?