Index: src/wp-includes/class-walker-category.php
===================================================================
--- src/wp-includes/class-walker-category.php	(revision 45926)
+++ src/wp-includes/class-walker-category.php	(working copy)
@@ -210,6 +210,7 @@
 				foreach ( $_current_terms as $_current_term ) {
 					if ( $category->term_id == $_current_term->term_id ) {
 						$css_classes[] = 'current-cat';
+						$link          = str_replace( '<a', '<a aria-current="page"', $link );
 					} elseif ( $category->term_id == $_current_term->parent ) {
 						$css_classes[] = 'current-cat-parent';
 					}
Index: src/wp-includes/general-template.php
===================================================================
--- src/wp-includes/general-template.php	(revision 45926)
+++ src/wp-includes/general-template.php	(working copy)
@@ -1734,18 +1734,19 @@
  * @return string HTML link content for archive.
  */
 function get_archives_link( $url, $text, $format = 'html', $before = '', $after = '', $selected = false ) {
-	$text = wptexturize( $text );
-	$url  = esc_url( $url );
+	$text         = wptexturize( $text );
+	$url          = esc_url( $url );
+	$aria_current = $selected ? ' aria-current="page"' : '';
 
-	if ( 'link' == $format ) {
+	if ( 'link' === $format ) {
 		$link_html = "\t<link rel='archives' title='" . esc_attr( $text ) . "' href='$url' />\n";
-	} elseif ( 'option' == $format ) {
+	} elseif ( 'option' === $format ) {
 		$selected_attr = $selected ? " selected='selected'" : '';
 		$link_html     = "\t<option value='$url'$selected_attr>$before $text $after</option>\n";
-	} elseif ( 'html' == $format ) {
-		$link_html = "\t<li>$before<a href='$url'>$text</a>$after</li>\n";
+	} elseif ( 'html' === $format ) {
+		$link_html = "\t<li>$before<a href='$url'$aria_current>$text</a>$after</li>\n";
 	} else { // custom
-		$link_html = "\t$before<a href='$url'>$text</a>$after\n";
+		$link_html = "\t$before<a href='$url'$aria_current>$text</a>$after\n";
 	}
 
 	/**
Index: src/wp-includes/widgets/class-wp-widget-recent-posts.php
===================================================================
--- src/wp-includes/widgets/class-wp-widget-recent-posts.php	(revision 45926)
+++ src/wp-includes/widgets/class-wp-widget-recent-posts.php	(working copy)
@@ -93,11 +93,16 @@
 		<ul>
 			<?php foreach ( $r->posts as $recent_post ) : ?>
 				<?php
-				$post_title = get_the_title( $recent_post->ID );
-				$title      = ( ! empty( $post_title ) ) ? $post_title : __( '(no title)' );
+				$post_title   = get_the_title( $recent_post->ID );
+				$title        = ( ! empty( $post_title ) ) ? $post_title : __( '(no title)' );
+				$aria_current = '';
+
+				if ( is_single() && get_the_ID() === $recent_post->ID ) {
+					$aria_current = ' aria-current="page"';
+				}
 				?>
 				<li>
-					<a href="<?php the_permalink( $recent_post->ID ); ?>"><?php echo $title; ?></a>
+					<a href="<?php the_permalink( $recent_post->ID ); ?>"<?php echo $aria_current; ?>><?php echo $title; ?></a>
 					<?php if ( $show_date ) : ?>
 						<span class="post-date"><?php echo get_the_date( '', $recent_post->ID ); ?></span>
 					<?php endif; ?>