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Advisory 26/2005: TinyMCE Compressor Vulnerabilities
From: Stefan Esser <sesser () hardened-php net>
Date: Thu, 29 Dec 2005 21:47:12 +0100
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-= Security Advisory =-
Advisory: TinyMCE Compressor Vulnerabilities
Release Date: 2005/12/29
Last Modified: 2005/12/29
Author: Stefan Esser [sesser () hardened-php net]
Application: TinyMCE Compressor <= 1.0.5
Applications that bundle it like Wordpress 2.0
Severity: Unchecked user input is directly used within filenames
or printed into the output buffer which allows disclosure
of arbitrary files and XSS attacks
Vendor Status: Vendor has released an updated version
editor control released as Open Source under LGPL by Moxiecode
Systems AB. It has the ability to convert HTML TEXTAREA fields or
other HTML elements to editor instances. TinyMCE is very easy to
integrate into other CMS systems.
The TinyMCE Compressor is a PHP script available by the TinyMCE
greatly increase the speed of TinyMCE.
A quick audit of the compressor script revealed that several
user supplied input variables are not checked and used directly to
construct filenames for files that are returned to the user.
Additionally some variables are directly printed to the request
body. This can be used by attackers to not only view files on the
server but also for Cross Site Scripting (XSS) attacks.
TinyMCE optionally comes with a PHP script that handles compression
speed of TinyMCE greatly. TinyMCE as HTML WYSIWYG editor is often
bundled with 3rd party applications, like the recently released
Wordpress 2.0 blogging software.
The TinyMCE compressor script allows the selection of things like
language, plugins, themes from within URL variables and does not
properly validate them. Because there is no check enforced on the
content of these variables it is possible to specify not only
illegal but also filenames outside of the dedicated directories.
It is only required to truncate the end of the filename with for
example an ASCII NUL. Which is for example not possible when the
server is running the latest version of the Hardening-Patch for PHP.
If the attacker succeeds in supplying a name of a file reachable by
the webserver user TinyMCE Compressor will print it's content into
the request body, leading to a file disclosure vulnerability. It
a file on the server and is able to include this file, that he can
use this for Cross Site Scripting (XSS) attacks.
Additionally to the file disclosure vulnerability variables like
'index' are directly printed into the request body and therefore
into the output. It is obvious that this leads to possible XSS
Proof of Concept:
The Hardened-PHP project is not going to release exploits for
this vulnerability to the public.
27. December 2005 - Disclosed vulnerability to vendor
27. December 2005 - During the following coffee break the
vendor response arrived
27. December 2005 - Five hours after our notification a
fixed version is released, unfortunately
the fix was incomplete
29. December 2005 - Vendor releases the corrected version
29. December 2005 - Public Disclosure
It is strongly recommended to upgrade to the new version of
TinyMCE Compressor which you can download at:
Additionally we recommend installing our Hardening-Patch for
PHP which makes part of the discovered vulnerabilities un-
pub 1024D/0A864AA1 2004-04-17 Hardened-PHP Signature Key
Key fingerprint = 066F A6D0 E57E 9936 9082 7E52 4439 14CC 0A86 4AA1
Copyright 2005 Stefan Esser. All rights reserved.
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- Advisory 26/2005: TinyMCE Compressor Vulnerabilities Stefan Esser (Dec 30)