diff --git a/wp-includes/class-wp-query.php b/wp-includes/class-wp-query.php
index a6c248a7bf..4be11581c4 100644
--- a/wp-includes/class-wp-query.php
+++ b/wp-includes/class-wp-query.php
@@ -529,7 +529,6 @@ class WP_Query {
 			, 'attachment'
 			, 'attachment_id'
 			, 'name'
-			, 'static'
 			, 'pagename'
 			, 'page_id'
 			, 'second'
@@ -764,7 +763,7 @@ 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 {
diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 74e27985b9..dee76c5acd 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -14,7 +14,7 @@ class WP {
 	 * @since 2.0.0
 	 * @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 a1f4d71db6..285bd5776f 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1613,6 +1613,11 @@ 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 ) && dirname( $target_parent ) !== $target_parent ) {
diff --git a/wp-includes/http.php b/wp-includes/http.php
index 0444792421..14172eeadb 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 01d3055d3e..ed573528c2 100644
--- a/wp-includes/pluggable.php
+++ b/wp-includes/pluggable.php
@@ -1079,7 +1079,7 @@ 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());
@@ -1097,7 +1097,7 @@ 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();
 	}
@@ -2645,4 +2645,3 @@ 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 82d856a063..c3dfe4af8c 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -544,7 +544,9 @@ function rest_send_cors_headers( $value ) {
 		header( 'Access-Control-Allow-Origin: ' . $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;