Let's suppose we believe our site to be secure because we've tested it on Windows and Mac and checked the flash doesn't cause issues, and we've tested it on mobile and the flash simply doesn't work. Now we need to test all over again.
Consider, for example, JPEG injection bugs. There are JPEGs embedded inside Flash content that are now being parsed by different code.
Let's suppose you're an ad network and you don't want to mistakenly inject malware into other websites because that would be bad. Now you need to think of a whole bunch of new cases. E.g. you might have carefully sanitized all the JPEGs on your site, but not the ones embedded in SWFs. This is merely an example.
Would it be a Good Thing if every copy of the Flash runtime magically disappeared and got replaced with this thing? Maybe. But as it is, life just got more, not less, complicated.
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.
Shumway decreases the attack surface of Firefox for general-purpose browsing: most people would install Flash otherwise, and this way that (infamously broad) attack vector is removed.
Ultimately, individual users have to take charge of their own individual attack surface. If switching from one Flash player to another increases their personal security, it's a good thing.
In general, I'd say replacing things with emulations of things is not a good way to get better reliability, performance, or security -- now you have bugs in the original thing and the emulation of the thing to consider.
In this case, the emulation lives within a restricted runtime environment and the real thing doesn't. But that's a performance / resource consumption / convenience / compatibility hit in exchange for "security", and those tend to fail simply because most people like their performance / resource consumption / convenience / compatibility.
thanks :) I, Gabe Newell and many others would like to see this happen.
Ironically most of the useful flash applications/games etc wouldn't run on these runtimes as they are using features not supported in HTML5. This sort of thing works best for crappy adverts and banners, which no one really wants anyway. This is highlighted by the fact the big competitor (Gordon?) is developed by the Google ad sense team ;)
And you remember who Gordon Shumway is right? ( https://en.wikipedia.org/wiki/ALF_(TV_series) )
I'm genuinely curious, as I do a bit of html5/webgl and formerly did a lot of flash/haxe, so I'm wondering what I missed...
However there are other things, like webcam/device support, some audio stuff, filters that may be very slow on a canvas and hard to run in WebGL inside other panes (overlays etc).
Users want to watch videos, they don't care about the technology under the hood.
Do you ever try and watch youtube videos that say, "this video isn't available on your device"...
https://news.ycombinator.com/item?id=6558539
I guess you could ask him for more details.
Unless you really loved the flash IDE which I guess some people do...