Directory traversal vulnerability in the get_lang function in global.php in Quicksilver Forums 1.4.2 and earlier, as used in QSF Portal before 1.4.5, when running on Windows, allows remote attackers to include and execute arbitrary local files via a "\" (backslash) in the lang parameter to index.php, which bypasses a protection mechanism that only checks for "/" (forward slash), as demonstrated by uploading and including PHP code in an avatar file.