Try esc escaping

Author: joedolson

src/wp-includes/blocks/categories.php

@@ -103,12 +103,15 @@ function build_dropdown_script_block_core_categories( $dropdown_id ) {
 	<script>
 	( function() {
 		var dropdown = document.getElementById( '<?php echo esc_js( $dropdown_id ); ?>' );
-		function onCatChange() {
+		function onCatChange(e) {
+			if ( 'keyup' === e.type && 'Escape' !== e.key ) {
+				return;
+			}
 			if ( dropdown.options[ dropdown.selectedIndex ].value !== -1 ) {
 				location.href = "<?php echo esc_url( home_url() ); ?>/?" + dropdown.name + '=' + dropdown.options[ dropdown.selectedIndex ].value;
 			}
 		}
-		dropdown.onchange = onCatChange;
+		dropdown.addEventListener( 'change', onCatChange(e) );
 	})();
 	</script>
 	<?php

src/wp-includes/widgets/class-wp-widget-categories.php

@@ -97,13 +97,16 @@ public function widget( $args, $instance ) {
 
 <script>
 (function() {
-	var dropdown = document.getElementById( "<?php echo esc_js( $dropdown_id ); ?>" );
-	function onCatChange() {
+	var dropdown = document.getElementById( '<?php echo esc_js( $dropdown_id ); ?>' );
+	function onCatChange(e) {
+		if ( 'keyup' === e.type && 'Escape' !== e.key ) {
+			return;
+		}
 		if ( dropdown.options[ dropdown.selectedIndex ].value > 0 ) {
 			dropdown.parentNode.submit();
 		}
 	}
-	dropdown.onchange = onCatChange;
+	dropdown.addEventListener( 'change', onCatChange(e) );
 })();
 </script>