Two forums, one on subdomain, one as main
 

Hey guys

I already did a lot of searching but most of the problems, people had their forums in different directories, here it is different subdomains.

I own a domain. Call it test.com. I recently accepted to host another forum on my server, gave them ce.test.com.
I then realized that my cookies end up on the other domain which is a security hole (I am sure they would not abuse anything but I want to do things right).
My Cookie domain is set to .test.com and their, well I dunno what their is.
Would I set mine to www.test.com? (I only use the www for my site, the other simply redirects to the www).
I tried setting mine to www.test.com and that worked, it's just really weird that some of the cookies now show up with the domain .www.test.com (they have another dot at the beginning). But I only set mine to www.test.com.
Am I doing it right?
It seems to work but it looks weird with the .www