full-disclosure - Re: IE handling the HTML notes incorrectly may lead to XSS attacks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Mon, 8 Aug 2011 09:50:56 +0200
From: Christian Sciberras <uuf6429@...il.com>
To: CnCxzSec衰仔 <cncxzhack@...il.com>
Cc: Full Disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: IE handling the HTML notes incorrectly may
 lead to XSS attacks

Javascript:

if(alert(1)); // executed
i(alert(1));  // not executed (TypeError: i is not a function)

It's worth to note that Firefox (5) does execute the inside function,
whereas Chrome (13) and IE(9) do not.
Talk about browser consistency...



On Mon, Aug 8, 2011 at 9:38 AM, CnCxzSec衰仔 <cncxzhack@...il.com> wrote:

>
> a good example to see the "incorrect handling":
> <!--[if<img/onerror=alert(1) src=]>   //executed.
> <!--[i<img/onerror=alert(1) src=]>    //not executed.
>
>
> On Mon, Aug 8, 2011 at 2:23 PM, Christian Sciberras <uuf6429@...il.com>wrote:
>
>> I think it's worth to note that MSIE expects an *expression* in the
>> conditional (it's a feature).
>> Hence even if you disable direct XSS, there still would probably be
>> more ways an *expression* could be used to write HTML code.
>>
>> As such, I don't think they should be "fixing" this (since it is
>> intended), but rather warn developers about it's existence.
>>
>> On the other hand, if developers are writing unfiltered HTML inside
>> this conditional, I think there are worse issues than this.
>> I've always believed in the philosophy of making browsers work as
>> expected instead of expecting them to comply and fix my issues.
>> Especially if the browser in question is Internet Explorer ;-).
>>
>> Cheers,
>> Chris.
>>
>>
>>
>> On Mon, Aug 8, 2011 at 5:59 AM, CnCxzSec衰仔 <cncxzhack@...il.com> wrote:
>> > 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@...il.com>
>> 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]-->
>> >
>> > _______________________________________________
>> > Full-Disclosure - We believe in it.
>> > Charter: http://lists.grok.org.uk/full-disclosure-charter.html
>> > Hosted and sponsored by Secunia - http://secunia.com/
>> >
>>
>
>

Content of type "text/html" skipped

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/