"This attack can be used to hijack Gmail/ Google doc cookies efficiently if certain conditions are met. The Google
docs are an integrated service provided by Google for online viewing the document. A user logged in to Gmail will
have the same cookie used for if any document. The interdependency can be exploited through this attack vector."

http://secniche.org/gmd_hijack/gc_hijack.xhtml

The issues were solved by Google in 5 days.

It is nice to notice that this cookie issue and this recent issue
http://blogoscoped.com/forum/154518.html

were reported to Google in responsible way.

Juha, but that has been fixed too.. Google Security Team propgated the fix on 05/07..!