Adjust post meta checks

Merges [40692] to the 4.2 branch.

Built from https://develop.svn.wordpress.org/branches/4.2@40698


git-svn-id: http://core.svn.wordpress.org/branches/4.2@40561 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-xmlrpc-server.php

@@ -332,6 +332,11 @@ class wp_xmlrpc_server extends IXR_Server {
 			if ( isset($meta['id']) ) {
 				$meta['id'] = (int) $meta['id'];
 				$pmeta = get_metadata_by_mid( 'post', $meta['id'] );
+
+				if ( ! $pmeta || $pmeta->post_id != $post_id ) {
+					continue;
+				}
+
 				if ( isset($meta['key']) ) {
 					$meta['key'] = wp_unslash( $meta['key'] );
 					if ( $meta['key'] !== $pmeta->meta_key )