The Xen pre-disclosure list is public, and Rackspace is on it:
http://www.xenproject.org/security-policy.html
They also spell out the policy for who is eligible.
http://www.xenproject.org/security-policy.html
They also spell out the policy for who is eligible.
Xen has previously had problems with people leaking embargoed security issues http://www.gossamer-threads.com/lists/xen/devel/248239