[whatwg] Comments on @sandbox
ian at hixie.ch
Tue Jan 12 00:16:36 PST 2010
On Thu, 5 Nov 2009, Adam Barth wrote:
> One interesting feature of @sandbox is that the hosting page can change
> the value of the sandbox attribute. Even though it's clear that having
> both allow-same-origin and allow-script at the *same* time lets the
> sandboxed content escape, it's probably less clear to folks that first
> setting allow-same-origin and then removing it and adding allow-script
> is also very dangerous.
> The reason is slightly subtle. Essentially, when the frame is in the
> allow-same-origin mode, it is very easy for the outer document to leak a
> frame enters the allow-script phase, the document can abuse the leaked
> object to XSS the outer page, as described in
> The reverse sequence is also dangerous because the inner page could use
> the techniques in this paper
> <http://www.adambarth.com/papers/2009/adida-barth-jackson.pdf> to build
> a fake DOM during the allow-scripts phase and confuse the outer page
> into XSSing itself in the allow-same-origin phase.
> To avoid these subtle traps for developers, I recommend to freezing the
> privileges of a sandboxed document at the time the document is loaded
> into the frame.
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
More information about the whatwg