Index: src/wp-admin/includes/class-wp-plugin-install-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-plugin-install-list-table.php	(revision 36269)
+++ src/wp-admin/includes/class-wp-plugin-install-list-table.php	(working copy)
@@ -461,7 +461,7 @@
 					case 'update_available':
 						if ( $status['url'] ) {
 							/* translators: 1: Plugin name and version */
-							$action_links[] = '<a class="update-now button" data-plugin="' . esc_attr( $status['file'] ) . '" data-slug="' . esc_attr( $plugin['slug'] ) . '" href="' . esc_url( $status['url'] ) . '" aria-label="' . esc_attr( sprintf( __( 'Update %s now' ), $name ) ) . '" data-name="' . esc_attr( $name ) . '">' . __( 'Update Now' ) . '</a>';
+							$action_links[] = '<a class="update-now button aria-button-if-js" data-plugin="' . esc_attr( $status['file'] ) . '" data-slug="' . esc_attr( $plugin['slug'] ) . '" href="' . esc_url( $status['url'] ) . '" aria-label="' . esc_attr( sprintf( __( 'Update %s now' ), $name ) ) . '" data-name="' . esc_attr( $name ) . '">' . __( 'Update Now' ) . '</a>';
 						}
 
 						break;
Index: src/wp-admin/js/updates.js
===================================================================
--- src/wp-admin/js/updates.js	(revision 36269)
+++ src/wp-admin/js/updates.js	(working copy)
@@ -524,6 +524,11 @@
 			e.preventDefault();
 			var $button = $( e.target );
 
+			// Do nothing while updating and when the button is disabled.
+			if ( $button.hasClass( 'updating-message' ) || $button.hasClass( 'button-disabled' ) ) {
+				return;
+			}
+
 			if ( wp.updates.shouldRequestFilesystemCredentials && ! wp.updates.updateLock ) {
 				wp.updates.requestFilesystemCredentials( e );
 			}