phpGB: cross site scripting bug

From: ppp-design (security@ppp-design.de)
Date: Mon Sep 09 2002 - 00:24:05 PDT

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    ppp-design found the following cross-site-scripting-bug in phpGB:
    
    
    Details
    - -------
    Product: phpGB
    Affected Version: 1.10 and maybe all versions before
    Immune Version: 1.20
    OS affected: all OS with php
    Vendor-URL: http://www.walzl.net
    Vendor-Status: informed, new version avaiable
    Security-Risk: high
    Remote-Exploit: Yes
    
    
    Introduction
    - ------------
    phpGB ist a php/mysql based guestbook. Unfortunately no input is been
    filtered for malicious code segments. That leads to the possibility of
     a cross-site-scripting attack.
    
    
    More details
    - ------------
    A possible blackhat is able to insert eg. javascript code into the
    guestbook entry. When an admin tries to delete this entry the script
    will be executed. So the attacke is able to eg. get the session id and
     enter the admin area without being authenticated.
    
    
    Proof-of-concept
    - ----------------
    Enter the following guestbookentry:
    
    "delete me <script>alert(document.cookie)</script>"
    
    When an admin tries to delete this entry, a popup showing his session
    id will come up. Of course it is quite easy to submit this session id
    to blackhat's server instead of showing this popup.
    
    
    Temporary-fix
    - -------------
    Filter all inputs for unwanted code segments like html or javascript code.
    
    
    Fix
    - ---
    phpGB 1.2 filters all inputs.
    
    
    Security-Risk
    - -------------
    Because after a successfull attack an attacker is able to do anything
    an admin can do, the whole guestbook shall be deemed to be
    compromised. That is why we are rating the risk to high.
    
    
    Vendor status
    - -------------
    The author had fixed this bug allready, when we informed him.
    
    
    Disclaimer
    - ----------
    All information that can be found in this advisory is believed to be
    true, but maybe it isn't. ppp-design can not be held responsible for
    the use or missuse of this information. Redistribution of this text is
    only permitted if the text has not been altered and the original
    author ppp-design (http://www.ppp-design.de) is mentioned.
    
    
    This advisory can be found online:
    http://www.ppp-design.de/advisories.php
    
    
    - --
    ppp-design
    http://www.ppp-design.de
    Public-Key: http://www.ppp-design.de/pgp/ppp-design.asc
    Fingerprint: 5B02 0AD7 A176 3A4F CE22  745D 0D78 7B60 B3B5 451A
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