[whatwg] HTML 5 : The Youtube response

Kornel Lesinski kornel at geekhood.net
Thu Jul 1 06:12:34 PDT 2010

> I believe we can allow arbitrary content to go fullscreen, along the lines of what Robert O'Callahan has proposed on this list, if we impose sufficient restrictions to mitigate the above risks. In my opinion, the following measures would likely be sufficient:
> A) Have a distinctive animated sequence when an element goes into full-screen mode. This helps the user understand what happened.
> B) Limit the ability to go fullscreen to user gestures, much as many browsers limit pop-ups. This prevents shenanigans from happening while the user is away from the keyboard, and greatly limits the potential annoyance factor.
> C) On systems with keyboard/mouse input, limit the keys that may be processed by fullscreen content to a small set, such as the set that Flash limits to in full-screen mode: <http://www.adobe.com/devnet/flashplayer/articles/fplayer10_security_changes_03.html#head5>.
> D) On multitouch devices with an onscreen keyboard as the normal means of input, things are trickier, because it's possible for a dedicated attacker to simulate the keyboard. My best idea is make sure that a visually distinctive status indicator appears at the top of the screen even in full-screen mode, since that is the norm on such platforms.
> E) Reserve one or more obvious key combinations to exiting fullscreen no matter what (Escape, perhaps Cmd+W/Ctrl+W).
> F) Even on keyboard/mouse type systems, have some distinctive visual affordance which is either always present or appears on mouse moves, and which allows the user to exit full-screen mode.
> I think these measures greatly mitigate risks (1) and (2) above, and open up highly valued functionality (full screen video) with a UI that users will enjoy, and customizability that video hosting sites will appreciate.

Another option (for low-res videos on desktop) might be to use lower screen resolution when in full screen — text and UI elements displayed by attacker will look noticeably different.

regards, Kornel

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