diff --git a/wp-includes/class-wp-query.php b/wp-includes/class-wp-query.php
index c0de352c2d..787240f9d1 100644
--- a/wp-includes/class-wp-query.php
+++ b/wp-includes/class-wp-query.php
@@ -582,7 +582,6 @@ class WP_Query {
 			, 'attachment'
 			, 'attachment_id'
 			, 'name'
-			, 'static'
 			, 'pagename'
 			, 'page_id'
 			, 'second'
@@ -811,7 +810,7 @@ class WP_Query {
 			// If year, month, day, hour, minute, and second are set, a single
 			// post is being queried.
 			$this->is_single = true;
-		} elseif ( '' != $qv['static'] || '' != $qv['pagename'] || !empty($qv['page_id']) ) {
+		} elseif ( '' != $qv['pagename'] || !empty($qv['page_id']) ) {
 			$this->is_page = true;
 			$this->is_single = false;
 		} else {
@@ -3048,7 +3047,15 @@ class WP_Query {
 			 */
 			$this->found_posts = $wpdb->get_var( apply_filters_ref_array( 'found_posts_query', array( 'SELECT FOUND_ROWS()', &$this ) ) );
 		} else {
-			$this->found_posts = count( $this->posts );
+			if ( is_array( $this->posts ) ) {
+				$this->found_posts = count( $this->posts );
+			} else {
+				if ( null === $this->posts ) {
+					$this->found_posts = 0;
+				} else {
+					$this->found_posts = 1;
+				}
+			}
 		}
 
 		/**
diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 63c7f0a2c6..fd3e08df50 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -15,7 +15,7 @@ class WP {
 	 * @access public
 	 * @var array
 	 */
-	public $public_query_vars = array('m', 'p', 'posts', 'w', 'cat', 'withcomments', 'withoutcomments', 's', 'search', 'exact', 'sentence', 'calendar', 'page', 'paged', 'more', 'tb', 'pb', 'author', 'order', 'orderby', 'year', 'monthnum', 'day', 'hour', 'minute', 'second', 'name', 'category_name', 'tag', 'feed', 'author_name', 'static', 'pagename', 'page_id', 'error', 'attachment', 'attachment_id', 'subpost', 'subpost_id', 'preview', 'robots', 'taxonomy', 'term', 'cpage', 'post_type', 'embed' );
+	public $public_query_vars = array( 'm', 'p', 'posts', 'w', 'cat', 'withcomments', 'withoutcomments', 's', 'search', 'exact', 'sentence', 'calendar', 'page', 'paged', 'more', 'tb', 'pb', 'author', 'order', 'orderby', 'year', 'monthnum', 'day', 'hour', 'minute', 'second', 'name', 'category_name', 'tag', 'feed', 'author_name', 'pagename', 'page_id', 'error', 'attachment', 'attachment_id', 'subpost', 'subpost_id', 'preview', 'robots', 'taxonomy', 'term', 'cpage', 'post_type', 'embed' );
 
 	/**
 	 * Private query variables.
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index c0bd2004b4..e95b7380fc 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1608,6 +1608,11 @@ function wp_mkdir_p( $target ) {
 	if ( file_exists( $target ) )
 		return @is_dir( $target );
 
+	// Do not allow path traversals.
+	if ( false !== strpos( $target, '../' ) || false !== strpos( $target, '..' . DIRECTORY_SEPARATOR ) ) {
+		return false;
+	}
+
 	// We need to find the permissions of the parent folder that exists and inherit that.
 	$target_parent = dirname( $target );
 	while ( '.' != $target_parent && ! is_dir( $target_parent ) ) {
diff --git a/wp-includes/http.php b/wp-includes/http.php
index 2c746a71db..c7e2d550dc 100644
--- a/wp-includes/http.php
+++ b/wp-includes/http.php
@@ -541,8 +541,9 @@ function wp_http_validate_url( $url ) {
 			$ip = $host;
 		} else {
 			$ip = gethostbyname( $host );
-			if ( $ip === $host ) // Error condition for gethostbyname()
-				$ip = false;
+			if ( $ip === $host ) { // Error condition for gethostbyname()
+				return false;
+			}
 		}
 		if ( $ip ) {
 			$parts = array_map( 'intval', explode( '.', $ip ) );
diff --git a/wp-includes/pluggable.php b/wp-includes/pluggable.php
index b7076fda8f..6b5c75c23b 100644
--- a/wp-includes/pluggable.php
+++ b/wp-includes/pluggable.php
@@ -1055,7 +1055,7 @@ if ( !function_exists('check_admin_referer') ) :
  *                   0-12 hours ago, 2 if the nonce is valid and generated between 12-24 hours ago.
  */
 function check_admin_referer( $action = -1, $query_arg = '_wpnonce' ) {
-	if ( -1 == $action )
+	if ( -1 === $action )
 		_doing_it_wrong( __FUNCTION__, __( 'You should specify a nonce action to be verified by using the first parameter.' ), '3.2.0' );
 
 	$adminurl = strtolower(admin_url());
@@ -1073,7 +1073,7 @@ function check_admin_referer( $action = -1, $query_arg = '_wpnonce' ) {
 	 */
 	do_action( 'check_admin_referer', $action, $result );
 
-	if ( ! $result && ! ( -1 == $action && strpos( $referer, $adminurl ) === 0 ) ) {
+	if ( ! $result && ! ( -1 === $action && strpos( $referer, $adminurl ) === 0 ) ) {
 		wp_nonce_ays( $action );
 		die();
 	}
@@ -2518,4 +2518,3 @@ function wp_text_diff( $left_string, $right_string, $args = null ) {
 	return $r;
 }
 endif;
-
diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index c83f9125b1..606a978797 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -528,7 +528,9 @@ function rest_send_cors_headers( $value ) {
 		header( 'Access-Control-Allow-Origin: ' . esc_url_raw( $origin ) );
 		header( 'Access-Control-Allow-Methods: OPTIONS, GET, POST, PUT, PATCH, DELETE' );
 		header( 'Access-Control-Allow-Credentials: true' );
-		header( 'Vary: Origin' );
+		header( 'Vary: Origin', false );
+	} elseif ( ! headers_sent() && 'GET' === $_SERVER['REQUEST_METHOD'] && ! is_user_logged_in() ) {
+		header( 'Vary: Origin', false );
 	}
 
 	return $value;