diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/class-walker-page.php
--- a/wp/wp-includes/class-walker-page.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/class-walker-page.php	Tue Dec 15 13:49:49 2020 +0100
@@ -122,15 +122,17 @@
 
 		if ( ! empty( $current_page ) ) {
 			$_current_page = get_post( $current_page );
-			if ( $_current_page && in_array( $page->ID, $_current_page->ancestors ) ) {
+
+			if ( $_current_page && in_array( $page->ID, $_current_page->ancestors, true ) ) {
 				$css_class[] = 'current_page_ancestor';
 			}
+
 			if ( $page->ID == $current_page ) {
 				$css_class[] = 'current_page_item';
-			} elseif ( $_current_page && $page->ID == $_current_page->post_parent ) {
+			} elseif ( $_current_page && $page->ID === $_current_page->post_parent ) {
 				$css_class[] = 'current_page_parent';
 			}
-		} elseif ( $page->ID == get_option( 'page_for_posts' ) ) {
+		} elseif ( get_option( 'page_for_posts' ) == $page->ID ) {
 			$css_class[] = 'current_page_parent';
 		}
 
@@ -151,7 +153,7 @@
 		$css_classes = $css_classes ? ' class="' . esc_attr( $css_classes ) . '"' : '';
 
 		if ( '' === $page->post_title ) {
-			/* translators: %d: ID of a post */
+			/* translators: %d: ID of a post. */
 			$page->post_title = sprintf( __( '#%d (no title)' ), $page->ID );
 		}
 
@@ -182,7 +184,7 @@
 
 		$attributes = '';
 		foreach ( $atts as $attr => $value ) {
-			if ( ! empty( $value ) ) {
+			if ( is_scalar( $value ) && '' !== $value && false !== $value ) {
 				$value       = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
 				$attributes .= ' ' . $attr . '="' . $value . '"';
 			}
@@ -199,7 +201,7 @@
 		);
 
 		if ( ! empty( $args['show_date'] ) ) {
-			if ( 'modified' == $args['show_date'] ) {
+			if ( 'modified' === $args['show_date'] ) {
 				$time = $page->post_modified;
 			} else {
 				$time = $page->post_date;