Update to Drupal 8.0.0-beta15. For more information, see: https://www.drupal.org/node/2563023

core/themes/seven/css/components/dialog.theme.css

@@ -7,9 +7,6 @@
   border: 0;
   position: absolute;
   z-index: 1260;
-  /* jQuery UI modals crash in Firefox unless overflow is set to hidden.
-     See: https://www.drupal.org/node/2423781 */
-  overflow: hidden;
   padding: 0;
 }
 @media all and (max-width: 48em) { /* 768px */

core/themes/seven/css/components/menus-and-lists.css

@@ -38,3 +38,7 @@ ul.inline li {
 ul.inline li {
   display: inline;
 }
+.item-list .item-list__comma-list,
+[dir="rtl"] .item-list .item-list__comma-list {
+  margin: 0;
+}