Steps to reproduce:
1. Start portal and login.
2. Admin > Content > MB > Post a new thread.
3. Copy any content from a txt file or word file.
4. Try to paste into the body of new thread.
Content could be pasted into body of thread.
Content can not be pasted into body of thread.
Note: This could be reproduced on chrome, FF, IE 11, but could not be reproduced on IE 9.