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Comment by Tloewald | Hacker News Reader

Well, we assume it's more secure than simply running Flash, but we don't know. In fact it increases the overall attack surface since now there's bugs in Adobe's implementation and bugs in this implementation to exploit.

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.

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Well this is counter to my understanding. As shumway - like PDF.js - is ultimately using the exact same rendering engine and scripting engine via the same interface and in the exact same way as the HTML pages are already exposing, the attack surface just got massively smaller. If there is a jpeg injection bug, its a bug in the browser proper.

It's smaller on browsers running this implementation of Flash but you're dealing with browsers running the real Flash runtime AND this new implementation, which may expose bugs you are not otherwise exposed to.

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.

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.

The attack surface isn't increased. If you can exploit the vulnerability using Shumway, you could also exploit the vulnerability using vanilla JS — because Shumway is just Javascript. Shumway doesn't allow new exploits that are impossible without Shumway.

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.

Fair enough. You have to be careful taking this argument too far, though, or you end up saying something like no other browser besides IE should be developed, because it increases the attack surface.

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.

Fair point. Any argument taken to extremes is probably a bad 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.

s/Windows/Linux/g

thanks :) I, Gabe Newell and many others would like to see this happen.

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