W3C home > Mailing lists > Public > public-html@w3.org > January 2010

Re: <iframe doc="">

From: Aryeh Gregor <Simetrical+w3c@gmail.com>
Date: Sun, 24 Jan 2010 15:42:22 -0500
Message-ID: <7c2a12e21001241242s3e53db1fm3fc19350d23fc29@mail.gmail.com>
To: Shelley Powers <shelley.just@gmail.com>
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, Ian Hickson <ian@hixie.ch>, "public-html@w3.org WG" <public-html@w3.org>
On Sun, Jan 24, 2010 at 11:55 AM, Shelley Powers <shelley.just@gmail.com> wrote:
> The same tools also provide the code to sanitize comments before
> they're posted.

This is not the case.  Every programming language includes a facility
by which you can trivially convert " to &quot; and & to &amp;.  None I
know of provides a facility to sanitize HTML, for any definition of
sanitize.  MediaWiki has more than a thousand lines of code to do
this.  Other software is probably less, since most software has much
stricter whitelists (e.g., limited or no CSS), but it's still not easy
at all to sanitize HTML.

It's almost impossible right now to just sit down and write some new
blog software that allows comments, without either 1) restricting them
to plaintext, or 2) risking security vulnerabilities.  HTML is a very
complicated format with lots of evil gotchas.  For instance, you might
think you can let comments through -- but then you just opened up
script execution in IE due to conditional comments.

<iframe sandbox> is a great way to fix that problem.  Together with
the seamless attribute and contenteditable, you could allow rich-text
blog comments with very little effort, and with no security risk.  But
having to make a separate document for each blog comment to link to
with <iframe src=""> is a pain in the neck, and also runs into risks
if someone gets a direct link to one of those documents.  So some way
to specify the sandboxed content inline is what's needed to make this
feature perfect.

Unfortunately, all possible ways to do that are horribly ugly.  You
can't use sane syntax like <iframe sandbox>literal sandboxed
text</iframe> because the author could just put in an <iframe>
himself.  And you can't ask authors to escape </iframe>, because
they'll forget; they're much less likely to forget to escape ",
because if they don't, content will break very quickly.  So you're
left with srcdoc="".  Which is pretty nasty, but I can't see a better
Received on Sunday, 24 January 2010 20:42:50 UTC

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