Well...no clue man, my config works:
/*
Copyright (c) 2003-2017, CKSource - Frederico Knabben. All rights reserved.
For licensing, see LICENSE.md or http://ckeditor.com/license
*/
CKEDITOR.editorConfig=function(a){a.toolbarGroups=[{name:"document",groups:["mode","document","doctools"]},{name:"clipboard",groups:["clipboard","undo"]},{name:"editing",groups:["find","selection","spellchecker"]},{name:"forms"},{name:"basicstyles",groups:["basicstyles","cleanup"]},{name:"paragraph",groups:["list","indent","blocks","align","bidi"]},{name:"links"},{name:"insert"},{name:"styles"},{name:"colors"},{name:"tools"},{name:"others"},{name:"about"}];a.removeButtons="Cut,Copy,Paste,Undo,Redo,Anchor,Underline,Strike,Subscript,Superscript";
a.removeDialogTabs="link:advanced"};
CKEDITOR.editorConfig = function( config ) {
config.extraPlugins = 'imgur';
config.imgurClientId = '123....';
};
What version of IPS are you using?