When viewing the sample page with embedded iFrames (here), Cognos will recognize that login has occurred and load the embedded content.

You can use this script with hardcoded credentials, for example if the content is on a specific user's account,
or you can use a login form so users can input their own credentials if the content is shared.

Sample Form to Login to Cognos Analytics Namespace (change to your own):

UserID:

Password: