Index: lams_tool_images/web/includes/javascript/imageGalleryitem.js
===================================================================
diff -u -r5ca819dd0f4447eb517ca030f301b2a4dbab544a -r0559504eae34958a1b85105cedeff10e591a52cf
--- lams_tool_images/web/includes/javascript/imageGalleryitem.js	(.../imageGalleryitem.js)	(revision 5ca819dd0f4447eb517ca030f301b2a4dbab544a)
+++ lams_tool_images/web/includes/javascript/imageGalleryitem.js	(.../imageGalleryitem.js)	(revision 0559504eae34958a1b85105cedeff10e591a52cf)
@@ -79,7 +79,17 @@
 			  // for server-side file type validation; consistent with CKEditor parameter
 			  'Type' : 'Image',
 			  'largeFilesAllowed' : true
-		  }
+		  },
+		  onBeforeFileAdded: function(currentFile, files) {
+			  var name = currentFile.data.name,
+			  	  extensionIndex = name.lastIndexOf('.'),
+			  	  valid = UPLOAD_ALLOWED_EXTENSIONS.includes(name.substring(extensionIndex).trim());
+			  if (!valid) {
+				  uppy.info(LABEL_NOT_ALLOWED_FORMAT, 'error', 10000);
+			  }
+			  
+			  return valid;
+	    }
 	  };
 	  
 	  switch(language) {