Error with CKeditor

Uncaught TypeError: Cannot read property ‘$’ of undefined
at CKEDITOR.focusManager.g (ckeditor_39a28802.min.js:224)
at CKEDITOR.focusManager. (ckeditor_39a28802.min.js:225)
at ckeditor_39a28802.min.js:26

how to upgrade the version of CKeditor to 4


Please avoid creating duplicate entries. There is already another thread about this, created by you.
Indico already uses CKeditor 4.
I’m closing this thread, feel free to answer on the other one.