diff --git src/wp-admin/js/updates.js src/wp-admin/js/updates.js
index 053aabc..b1ea87f 100644
--- src/wp-admin/js/updates.js
+++ src/wp-admin/js/updates.js
@@ -2087,7 +2087,7 @@
 
 			$.support.postMessage = !! window.postMessage;
 
-			if ( false === $.support.postMessage || null === target ) {
+			if ( false === $.support.postMessage || null === target || -1 !== window.parent.location.pathname.indexOf( 'update-core.php' ) ) {
 				return;
 			}