Cross Domain Cookies With FormsAuthentication

Question

I know the security risk associated and have brought it up with the business, but they want to have their 5 domains to share the login cookie.

We are using and have

Answer 1

Not only with ASP.Net is this not possible, but not at all. Cookies are always domain-specific - no commercial browser will work any other way. This is by design and very much necessary to prevent widespread abuse of cookies. Muerte pointed you into the right direction (single sign-on).