Internet Explorer 5.1 for Macintosh allows remote attackers to bypass security checks and invoke local AppleScripts within a specific HTML element, aka the "Local Applescript Invocation" 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.