Missing file in whitelist: /core/ext/ckeditor4/js/ck-options.json
I found this issue when I tried to edit the configuration of CKEditor here: /civicrm/admin/ckeditor
The select box for advanced options is missing here because the file /core/ext/ckeditor4/js/ck-options.json could not be loaded. It is not copied into my public library folder by this plugin.