Editor: Fix Path Traversal issue on Windows in Template-Part Block.

Props xknown.




git-svn-id: https://develop.svn.wordpress.org/trunk@58470 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.php

@@ -6199,6 +6199,9 @@ function validate_file( $file, $allowed_files = array() ) {
 		return 0;
 	}
 
+	// Normalize path for Windows servers
+	$file = wp_normalize_path( $file );
+
 	// `../` on its own is not allowed:
 	if ( '../' === $file ) {
 		return 1;