Recent App Test

[<ramatkal () hotmail com>]

During a recent Application pen test I came across a url of the form:
 
http://www.vulnsite.com/cgi-bin/vulnscript.jsp?url=www.website.com&id=12345
 
I changed the url parameter to something like url=www.google.com and google appeared in my browser. Next, i changed the 
url to url=www.whatismyip.com, hoping that the ip address of the webserver would be displayed, however, only my ip 
address was displayed.

This means that my browser is loading the url parameter as opposed to the webserver script fethching the url and then 
displaying it for me in my browser right? Is this a security issue?


Assuming that it was the actual webserver script fetching the url parameter and then displaying it for me, I've come up 
with a few vulnerabilities (listed below) and was hoping that people might like to share some of their ideas.
   
1) Can use vulnsite as a proxy (& hack other sites)
2) Can port scan using the vuln site by changing url=www.website.com to url=www.sitetoscan.com:port
3) Can connect to & port scan machines behind the firewall.
 

Thanks in adance,
Sol