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TUCoPS :: Browsers :: expl5564.htm

Internet Explorer w/ Outlook Express fooled into file execution (again)



29th Jul 2002 [SBWID-5564]
COMMAND

	IE w/ Outlook Express fooled into file execution (again)

SYSTEMS AFFECTED

	 Internet Explorer 6.00. 

	 Outlook Express 6.00

	

PROBLEM

	http-equiv [http-equiv@excite.com] [http://www.malware.com] found :
	

	Trivial lead-up to yet another silent delivery and  installation  of  an
	executable on the target computer using Outlook Express 6. This  can  be
	achieved  combining  several  past   possibilities,   specifically   the
	following:
	

	http://www.securityfocus.com/bid/1033

	http://www.securityfocus.com/bid/2456

	http://www.securityfocus.com/bid/4387 

	

	And:
	

	XML. In order to achieve the required results as outlined in the  above,
	we must determine the location of  the  Temporary  Internet  File  [TIF]
	folders. This can only be achieved if we  can  physically  open  up  our
	file from within and read its location. Technically  that  can  only  be
	achieved  if  we  have  a  security  dialogue  prompt  asking   us   for
	permission. For security reasons all embedded  and  attached  files  are
	transferred to the TIF upon opening the mail message.  If  we  elect  to
	open the file through acceptance of the security  warning  dialogue,  it
	is opened from within the TIF by whatever  program  is  associated  with
	that file.
	

	Okay:
	

	Okay. XML. XML files are associated with Internet Explorer. It  utilises
	an XML parser to parse the file for display in Internet Explorer.  These
	files are peculiar little files that require an additional  file  called
	a style sheet [*.xsl] in order to process  scripting  and  html.  To  do
	that, the file must be 'linked' to the XML file like so:
	

	 <?xml version="1.0"?> 

	<?xml-stylesheet type="text/xsl" href="malware.xsl" ?> 

	

	where malware.xsl can contain our scripting and html.
	

	And:
	

	Well, for security purposes linking to a remote  *.xsl  fle  is  denied:
	"permission denied", so instead we force our  scripting  and  html  into
	the XML file and into the XML parser directly:
	

	<?xml version="1.0" ?>

	<?xml-stylesheet type="text/css" 

	href="http://www.malware.com/malware.css" ?>

	<malware>

	

	<h4 style="position: absolute;top:39;left:expression(alert

	(document.location));font-family:arial;font-size:12pt;BACKGROUND-

	IMAGE:url('http://www.malware.com/youlickit.gif');background-

	repeat:no-repeat;background-position: 100 30;z-index:-

	100;height:200pt;width:400pt;font-family:Verdana;color:red">sure it 

	can, malware says so</h4>

	</malware>

	

	What this does is generate an error in the XML  parser  along  with  our
	html and scripting, and as a consequence,  having  the  file  opened  up
	from within the TIF by Internet Explorer, we  are  once  again  able  to
	determine our TIF location. Couple that  with  the  aforementioned  past
	possibilities and we are once again in business.
	

	Working Example:
	

	http://www.malware.com/cannotindeed.zip

	

	Screen shot:
	

	http://www.malware.com/x-ma.png

	

	

	Important Notes:
	

	1.On several test machines, recollection is foggy as to  default  status
	of *.xml in mail. Possibility is that 'confirm open after  download'  is
	not default.
	

	2. On several test occasions, scripting was fired in mail  and  remotely
	on the web  site  despite  'active  scripting  off'  both,  however  not
	reproducible consistentantly and may be related to processor  speed  and
	xml parser delay in parsing combination.
	

	3. Test  series  of  win98  machines,  Internet  Explorer  6.0.2600  and
	Outlook Express 6.0.2600 bandages and all
	

	4. None.

SOLUTION

	?


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