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common/lib/xmodule/xmodule/js/src/html/edit.coffee

@@ -11,6 +11,9 @@ class @HTMLEditingDescriptor
     })
 
     $(@advanced_editor.getWrapperElement()).addClass(HTMLEditingDescriptor.isInactiveClass)
+
+#   This is a workaround for the fact that tinyMCE's baseURL property is not getting correctly set on AWS
+#   instances (like sandbox). It is not necessary to explicitly set baseURL when running locally.
     tinyMCE.baseURL = window.location.protocol + "//" + window.location.host + '/static/js/vendor/tiny_mce'
     @tiny_mce_textarea = $(".tiny-mce", @element).tinymce({
       script_url : '/static/js/vendor/tiny_mce/tiny_mce.js',