Microsoft Internet Explorer 5.01 and 6 allows certain script to persist across navigations between pages, which allows remote attackers to obtain the window location of visited web pages in other domains or zones, aka "Window Location Information Disclosure Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A171
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2006/ms06-042
http://www.vupen.com/english/advisories/2006/3212
http://www.securityfocus.com/bid/19339