I have most things working OK in IE11 (Windows 8.1), except when trying to insert a link or a picture.
I turned on debugging with F12, and it showed the following error (screen shot attached).
Any other user using IE11/Windows 8.1 to confirm?
I have the SmartScreen filter turned off in IE.
All OK in Chrome and Firefox.

Does it happen on latest
Does it happen on latest major: https://github.com/ckeditor/ckeditor-dev/tree/major?
CKEditor 4.2.2 (latest version ATM) does not support IE11 yet. CKEditor 4.3 (will be released next week) and you can check it on the major branch.
Piotrek (Reinmar) Koszuliński
CKEditor JavaScript Developer
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