Microsoft Internet Explorer 4.0 through 6.0 could allow local users to differentiate between alphanumeric and non-alphanumeric characters used in a password by pressing certain control keys that jump between non-alphanumeric characters, which makes it easier to conduct a brute-force password guessing attack.

A function in Internet Explorer 4.x and 5.x does not properly verify the domain of a frame within a browser window, which allows a remote attacker to read client files, aka a variant of the "Frame Domain Verification" vulnerability.

Internet Explorer 4.x and 5.x does not properly re-validate an SSL certificate if the user establishes a new SSL session with the same server during the same Internet Explorer session, aka one of two different "SSL Certificate Validation" vulnerabilities.

Internet Explorer 4.x and 5.x does not properly verify all contents of an SSL certificate if a connection is made to the server via an image or a frame, aka one of two different "SSL Certificate Validation" vulnerabilities.