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Re: HTML imports: new XSS hole?

From: Robin Berjon <robin@w3.org>
Date: Tue, 03 Jun 2014 16:58:28 +0200
Message-ID: <538DE294.5080502@w3.org>
To: Boris Zbarsky <bzbarsky@MIT.EDU>, public-webapps@w3.org
On 02/06/2014 15:08 , Boris Zbarsky wrote:
> On 6/2/14, 9:02 AM, James M Snell wrote:
>> I suppose that If you
>> needed the ability to sandbox them further, just wrap them inside a
>> sandboxed iframe.
> The worry here is sites that currently have html filters for
> user-provided content that don't know about <link> being able to run
> scripts.  Clearly once a site knows about this they can adopt various
> mitigation strategies.  The question is whether we're creating XSS
> vulnerabilities in sites that are currently not vulnerable by adding
> this functionality.
> P.S. A correctly written whitelist filter will filter these things out.
>   Are we confident this is standard practice now?

I haven't bumped into a blacklist filter in a *long* while. I suspect 
that any that might exist will be hand-rolled and not part of any 
platform. The odds are pretty strong that they're already unsafe if not 
wide open.

So I would say there's a risk, but not a huge one. That said, I still 
prefer Simon's approach.

PS: I've been wondering if adding an HTML sanitiser to the platform 
might make sense.

Robin Berjon - http://berjon.com/ - @robinberjon
Received on Tuesday, 3 June 2014 15:03:09 UTC

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