Internet Explorer 4.0 and 5.0 allows a malicious web site to obtain client cookies from another domain by including that domain name and escaped characters in a URL, aka the "Unauthorized Cookie Access" vulnerability.

Internet Explorer 5.0 and 5.01 allows remote attackers to bypass the cross frame security policy and read files via the external.NavigateAndFind function.

By default, Internet Explorer 5.0 and other versions enables the "Navigate sub-frames across different domains" option, which allows frame spoofing.

Internet Explorer 3.x to 4.01 allows a remote attacker to insert malicious content into a frame of another web site, aka frame spoofing.

Internet Explorer 3 records a history of all URL's that are visited by a user in DAT files located in the Temporary Internet Files and History folders, which are not cleared when the user selects the "Clear History" option, and are not visible when the user browses the folders because of tailored displays.

JavaScript in Internet Explorer 3.x and 4.x, and Netscape 2.x, 3.x and 4.x, allows remote attackers to monitor a user's web activities, aka the Bell Labs vulnerability.