From c86ee39ff4c1a79b93c967eb88522f5c09614a28 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Wed, 4 Sep 2019 16:57:56 +0000
Subject: [PATCH] Improve URL validation in `wp_validate_redirect()`.

Props vortfu, whyisjake, peterwilsoncc.
Built from https://develop.svn.wordpress.org/trunk@45971


git-svn-id: http://core.svn.wordpress.org/trunk@45782 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/pluggable.php | 8 ++++++++
 wp-includes/version.php   | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/wp-includes/pluggable.php b/wp-includes/pluggable.php
index 82b55f199a..9336e03c7e 100644
--- a/wp-includes/pluggable.php
+++ b/wp-includes/pluggable.php
@@ -1407,6 +1407,14 @@ if ( ! function_exists( 'wp_validate_redirect' ) ) :
 			return $default;
 		}
 
+		if ( ! isset( $lp['host'] ) && ! empty( $lp['path'] ) && '/' !== $lp['path'][0] ) {
+			$path = '';
+			if ( ! empty( $_SERVER['REQUEST_URI'] ) ) {
+				$path = dirname( parse_url( 'http://placeholder' . $_SERVER['REQUEST_URI'], PHP_URL_PATH ) . '?' );
+			}
+			$location = '/' . ltrim( $path . '/', '/' ) . $location;
+		}
+
 		// Reject if certain components are set but host is not. This catches urls like https:host.com for which parse_url does not set the host field.
 		if ( ! isset( $lp['host'] ) && ( isset( $lp['scheme'] ) || isset( $lp['user'] ) || isset( $lp['pass'] ) || isset( $lp['port'] ) ) ) {
 			return $default;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index d31146053c..c281d10c03 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45964';
+$wp_version = '5.3-alpha-45971';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.