A logout feature of a service that facilitates login to multiple domain
websites maintains a list of the sites that a user logs on to during a
session and completely logs the user out of all the sites they visited
during the session. A data structure in the form of a cookie named
"Visited Sites" is used by a login server to maintain a list of all sites
that a user logs on to during a session. When the user selects a logout
link anywhere on the network, they are directed to a logout page on the
login server. The login server retires all login domain cookies first,
and displays a page that explains to the user that they are about to be
logged out of each domain. The logout page generates image tags for each
of the sites listed in the visited-sites cookie. The image tag provides a
URL hosted at each site that expires any Passport cookies that are
present at the site.