--- a/wp/wp-admin/js/accordion.js	Tue Jun 09 11:14:17 2015 +0000
+++ b/wp/wp-admin/js/accordion.js	Mon Oct 14 17:39:30 2019 +0200
@@ -53,7 +53,10 @@
 	 */
 	function accordionSwitch ( el ) {
 		var section = el.closest( '.accordion-section' ),
-			siblings = section.closest( '.accordion-container' ).find( '.open' ),
+			sectionToggleControl = section.find( '[aria-expanded]' ).first(),
+			container = section.closest( '.accordion-container' ),
+			siblings = container.find( '.open' ),
+			siblingsToggleControl = siblings.find( '[aria-expanded]' ).first(),
 			content = section.find( '.accordion-section-content' );
 
 		// This section has no content and cannot be expanded.
@@ -61,15 +64,30 @@
 			return;
 		}
 
+		// Add a class to the container to let us know something is happening inside.
+		// This helps in cases such as hiding a scrollbar while animations are executing.
+		container.addClass( 'opening' );
+
 		if ( section.hasClass( 'open' ) ) {
 			section.toggleClass( 'open' );
 			content.toggle( true ).slideToggle( 150 );
 		} else {
+			siblingsToggleControl.attr( 'aria-expanded', 'false' );
 			siblings.removeClass( 'open' );
 			siblings.find( '.accordion-section-content' ).show().slideUp( 150 );
 			content.toggle( false ).slideToggle( 150 );
 			section.toggleClass( 'open' );
 		}
+
+		// We have to wait for the animations to finish
+		setTimeout(function(){
+		    container.removeClass( 'opening' );
+		}, 150);
+
+		// If there's an element with an aria-expanded attribute, assume it's a toggle control and toggle the aria-expanded value.
+		if ( sectionToggleControl ) {
+			sectionToggleControl.attr( 'aria-expanded', String( sectionToggleControl.attr( 'aria-expanded' ) === 'false' ) );
+		}
 	}
 
 })(jQuery);