After you copy content from an http webpage to an https webpage in Internet Explorer 11, the webpage editor on the https webpage is unusable.
To resolve this problem, install the most recent cumulative security update for Internet Explorer. To do this, go to Microsoft Update. Additionally, see the technical information about the most recent cumulative security update for Internet Explorer.
Note This update was first included in March cumulative security update for Internet Explorer (MS15-018).
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
See the terminology that Microsoft uses to describe software updates.