Ticket #39859: patch.diff

src/wp-includes/js/media/views/modal.js

@@ -123 +123 @@
                         }
                 }
 
+                var initialX = window.scrollX, initialY = window.scrollY;
                 this.$el.focus();
+                window.scrollTo(initialX, initialY);
 
                 return this.propagate('open');
         },