baseDir has to be the whole path to work with shared directories below the root directory.

apps/files_sharing/public.php

@@ -25,7 +25,7 @@ if (isset($_GET['file']) || isset($_GET['dir'])) {
 	if (isset($_GET['dir'])) {
 		$type = 'folder';
 		$path = $_GET['dir'];
-		$baseDir = basename($path);
+		$baseDir = $path;
 		$dir = $baseDir;
 	} else {
 		$type = 'file';