It might be true that as an ad network if you allow Flash files, but don't allow JS files, your life might become harder. (If you do allow JS files, your life i

It might be true that as an ad network if you allow Flash files, but don't allow JS files, your life might become harder. (If you do allow JS files, your life is no different — you were already exposed to JS vulnerabilities). As a user, though, your browser is significantly more secure running Shumway than running Flash. It literally removes an entire attack vector without adding a new one. If there's an exploitable vulnerability in Firefox's JS engine, you're vulnerable to it regardless of whether you run Shumway or not — but if there's an exploitable vulnerability in Flash, you aren't vulnerable if you're running Shumway instead.