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.
https://exchange.xforce.ibmcloud.com/vulnerabilities/4624
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-039
http://www.securityfocus.com/bid/1309