Index: lams_admin/web/import/importGroups.jsp
===================================================================
diff -u -r80371e446858031dcb9d7fa4456a79e8ab71693c -r0559504eae34958a1b85105cedeff10e591a52cf
--- lams_admin/web/import/importGroups.jsp	(.../importGroups.jsp)	(revision 80371e446858031dcb9d7fa4456a79e8ab71693c)
+++ lams_admin/web/import/importGroups.jsp	(.../importGroups.jsp)	(revision 0559504eae34958a1b85105cedeff10e591a52cf)
@@ -52,24 +52,35 @@
 		 * Initialise Uppy as the file upload widget
 		 */
 		function initFileUpload(tmpFileUploadId, language) {
-			  var uppyProperties = {
-				  // upload immediately 
-				  autoProceed: true,
-				  allowMultipleUploads: true,
-				  debug: false,
-				  restrictions: {
-					// taken from LAMS configuration
-				    maxFileSize: +UPLOAD_FILE_MAX_SIZE,
-				    maxNumberOfFiles: 1,
-				    allowedFileTypes : ['.xls']
-				  },
-				  meta: {
-					  // all uploaded files go to this subdir in LAMS tmp dir
-					  // its format is: upload_<userId>_<timestamp>
-					  'tmpFileUploadId' : tmpFileUploadId,
-					  'largeFilesAllowed' : true
-				  }
-			  };
+			var allowedFileTypes = ['.xls'],
+	  	  		uppyProperties = {
+					  // upload immediately 
+					  autoProceed: true,
+					  allowMultipleUploads: true,
+					  debug: false,
+					  restrictions: {
+						// taken from LAMS configuration
+					    maxFileSize: +UPLOAD_FILE_MAX_SIZE,
+					    maxNumberOfFiles: 1,
+					    allowedFileTypes : allowedFileTypes
+					  },
+					  meta: {
+						  // all uploaded files go to this subdir in LAMS tmp dir
+						  // its format is: upload_<userId>_<timestamp>
+						  'tmpFileUploadId' : tmpFileUploadId,
+						  'largeFilesAllowed' : true
+					  },
+					  onBeforeFileAdded: function(currentFile, files) {
+						  var name = currentFile.data.name,
+						  	  extensionIndex = name.lastIndexOf('.'),
+						  	  valid = allowedFileTypes.includes(name.substring(extensionIndex).trim());
+						  if (!valid) {
+							  uppy.info('<fmt:message key="error.attachment.not.xls" />', 'error', 10000);
+						  }
+						  
+						  return valid;
+				    }
+				  };
 			  
 			  switch(language) {
 			  	case 'es' : uppyProperties.locale = Uppy.locales.es_ES; break; 
@@ -94,6 +105,10 @@
 				  height: 150,
 				  width: '100%'
 				});
+
+			  uppy.use(Uppy.Informer, {
+				  target: '#file-upload-area'
+			  });
 			  
 			  uppy.use(Uppy.StatusBar, {
 				  target: '#file-upload-area',