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Geeklog XSS and CRLF Injection
From: full-disclosure () lists netsys com (Ulf Harnhammar)
Date: Fri, 19 Jul 2002 02:23:52 +0200 (CEST)

Geeklog XSS and CRLF Injection

PROGRAM: Geeklog
VENDOR: Tony Bibbs et al. <geeklog-devel () lists sourceforge net>
HOMEPAGE: http://geeklog.sourceforge.net/
VULNERABLE VERSIONS: 1.3.5sr1, possibly earlier versions as well


"Geeklog is a 'blog', otherwise known as a Weblog. It allows
you to create your own virtual community area, complete with user
administration, story posting, messaging, comments, polls, calendar,
weblinks, and more! It can run on many different operating systems,
and uses PHP4 and MySQL."

(direct quote from the program's homepage)

Geeklog is published under the terms of the GNU General Public


1) Geeklog has got an XSS hole that affects both the stories and
the comments. The program removes the HTML elements that are used
for scripting, but it fails to remove the HTML attributes that are
used for the same purpose, which leads to this hole.

One example of an XSS attack would be:

<b onMouseOver="self.location.href='http://localhost/geeklog/'";>life
has made her that much bolder now</b>

When a victim moves the mouse pointer over the quote from "Lady
Godiva's Operation", an intrinsic event occurs and the JavaScript
code is executed.

(There is also an XSS issue in the search engine. It was reported
by ┬žome1, and not by me.)

2) Geeklog has got a CRLF Injection hole in User Profile: Send
Email. The users' mail addresses are meant to be secret, but by
using this hole, you can get someone's mail address anyway.

The problem is that you can add extra mail headers, by using a
CRLF combination followed by an extra mail header in the Subject
field. One way to add them is saving the HTML document with the
form, and changing the <input type=text name=subject> tag to a
textarea. After opening the edited document in a web browser, you
enter a Subject line in the textarea, press Enter, and then you
enter your extra mail header. When the mail is sent, that header
will be included. If the header in question is "Bcc: <your own
mail address>", the message will silently be copied to you, thus
revealing the recipient's mail address without them knowing.

I have described this type of problem in further detail
in my "CRLF Injection" paper, which is available at


The vendor was contacted on the 1st of July. Version 1.3.5sr2,
which does not have any of these security holes (neither mine nor
┬žome1's), was released on the 9th of July.


I recommend that all administrators upgrade to version 1.3.5sr2.

// Ulf Harnhammar
ulfh () update uu se

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