diff -r 34716fd837a4 -r be944660c56a wp/wp-includes/js/customize-base.js
--- a/wp/wp-includes/js/customize-base.js	Tue Dec 15 15:52:01 2020 +0100
+++ b/wp/wp-includes/js/customize-base.js	Wed Sep 21 18:19:35 2022 +0200
@@ -112,8 +112,8 @@
 	 * @param object staticProps Properties to apply directly to the class.
 	 * @return child The subclass.
 	 */
-	api.Class.extend = function( protoProps, classProps ) {
-		var child = inherits( this, protoProps, classProps );
+	api.Class.extend = function( protoProps, staticProps ) {
+		var child = inherits( this, protoProps, staticProps );
 		child.extend = this.extend;
 		return child;
 	};
@@ -197,7 +197,7 @@
 
 			$.extend( this, options || {} );
 
-			this.set = $.proxy( this.set, this );
+			this.set = this.set.bind( this );
 		},
 
 		/*
@@ -501,7 +501,7 @@
 				dfd  = $.Deferred();
 
 			// If the last argument is a callback, bind it to .done().
-			if ( $.isFunction( ids[ ids.length - 1 ] ) ) {
+			if ( typeof ids[ ids.length - 1 ] === 'function' ) {
 				dfd.done( ids.pop() );
 			}
 
@@ -609,7 +609,7 @@
 			};
 
 			this.bind( this.update );
-			this.element.bind( this.events, this.refresh );
+			this.element.on( this.events, this.refresh );
 		},
 
 		find: function( selector ) {
@@ -734,7 +734,7 @@
 			 * This will prevent every Messenger's receive function from being
 			 * unbound when calling $.off( 'message', this.receive );
 			 */
-			this.receive = $.proxy( this.receive, this );
+			this.receive = this.receive.bind( this );
 			this.receive.guid = $.guid++;
 
 			$( window ).on( 'message', this.receive );