Re: [Full-disclosure] IE handling the HTML notes incorrectly may lead to XSS attacks

[CnCxzSec衰仔 <cncxzhack@xxxxxxxxx>]

this is a normal use, but <!--[if<img/onerror=alert(1) src=]> is an unnormal
use. IE should regard this as an HTML comment instead of a downlevel-hidden
comment, so the HTML tags inside the COMMENT should not be evaled.

On Mon, Aug 8, 2011 at 11:30 AM, Andrew Farmer <andfarm@xxxxxxxxx> wrote:

> On 2011-08-07, at 19:53, CnCxzSec衰仔 wrote:
> > hi all, here is an interesting trick to perform an xss attack with IE
> > browsers.
> >
> > some rich text applications such as email and blog, may provide HTML uses
> > but have a policy to block the on-event execution to prevent the XSS
> attack.
> > However, this applications may also allow the HTML notes uses,for
> instance
> > "<!--  -->"
>
> Any such applications are likely to also be vulnerable to a simpler attack
> based on "downlevel-hidden" conditional comments:
>
> <!--[if IE]>
> <script>anything you want can go here, presumably</script>
> <![endif]-->

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