Index: lams_central/web/ckeditor/plugins/equation/plugin.js
===================================================================
diff -u -re215b142c7d6806421645b25dbd5a45a23c129bc -r39d2c0d94cc4c6401d7507a65ca51d10e048612e
--- lams_central/web/ckeditor/plugins/equation/plugin.js	(.../plugin.js)	(revision e215b142c7d6806421645b25dbd5a45a23c129bc)
+++ lams_central/web/ckeditor/plugins/equation/plugin.js	(.../plugin.js)	(revision 39d2c0d94cc4c6401d7507a65ca51d10e048612e)
@@ -29,7 +29,12 @@
 			//open a popup window when the button is clicked
 			if (popupEqnwin==null || popupEqnwin.closed || !popupEqnwin.location) 
 			{
-				var url='http://latex.codecogs.com/editor_json3.php?type=url&editor=CKEditor';
+				// LDEV-3281: fixing protocol
+				var protocol = "http:";
+				if (window.location.protocol == "https:") {
+					var protocol = "https:";
+				}
+				var url=protocol+'//latex.codecogs.com/editor_json3.php?type=url&editor=CKEditor';
 		
 				//if(language!='') url+='&lang='+language;
 				if(latex!==undefined)