diff --git a/wp-admin/about.php b/wp-admin/about.php
index 1fb05b94b1..2b097ed626 100644
--- a/wp-admin/about.php
+++ b/wp-admin/about.php
@@ -39,7 +39,10 @@ include( ABSPATH . 'wp-admin/admin-header.php' );
 </h2>
 
 <div class="changelog point-releases">
-	<h3><?php echo _n( 'Maintenance and Security Release', 'Maintenance and Security Releases', 20 ); ?></h3>
+	<h3><?php echo _n( 'Maintenance and Security Release', 'Maintenance and Security Releases', 21 ); ?></h3>
+	<p><?php printf( __( '<strong>Version %s</strong> addressed one security issue.' ), '3.9.21' ); ?>
+		<?php printf( __( 'For more information, see <a href="%s">the release notes</a>.' ), 'https://codex.wordpress.org/Version_3.9.21' ); ?>
+	</p>
 	<p><?php printf( _n( '<strong>Version %1$s</strong> addressed a security issue.',
 			'<strong>Version %1$s</strong> addressed some security issues.', 7 ), '3.9.20' ); ?>
 		<?php printf( __( 'For more information, see <a href="%s">the release notes</a>.' ), 'https://codex.wordpress.org/Version_3.9.20' ); ?>
diff --git a/wp-includes/version.php b/wp-includes/version.php
index d5924e748a..ab02fd4f37 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '3.9.20';
+$wp_version = '3.9.21';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.