Use data(...) rather than hidden span

common/lib/xmodule/xmodule/js/src/sequence/display.coffee

@@ -3,8 +3,7 @@ class @Sequence
     @el = $(element).find('.sequence')
     @contents = @$('.seq_contents')
     @id = @el.data('id')
-    @modx_url = @$('#course_modx_root').text()
-    @modx_url = @modx_url.substr(1,@modx_url.length-2) # Remove enclosing quotes
+    @modx_url = @el.data('course_modx_root')
     @initProgress()
     @bind()
     @render parseInt(@el.data('position'))

lms/templates/seq_module.html

-<div id="sequence_${element_id}" class="sequence" data-id="${item_id}" data-position="${position}" >
-  <span style="display:none" id="course_modx_root">"/course/modx"</span>
+<div id="sequence_${element_id}" class="sequence" data-id="${item_id}" data-position="${position}" data-course_modx_root="/course/modx" >
   <nav aria-label="Section Navigation" class="sequence-nav">
     <ol id="sequence-list">
       % for idx, item in enumerate(items):