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 <[email protected]> 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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