Dynamics CRM Set IFrame to a Blank URL

When adding an IFrame to an entity form, Dynamics CRM requires that a default URL be defined. When we do not know the URL at design time, we commonly would just set the URL to the string about:blank. When we type this on a browser, this basically tells the browser to load an empty HTML page which is the ideal approach when the URL should be defined dynamically. The problem is that when we...