Cross-site scripting (XSS) vulnerability in Multiple Time Sheets (MTS) 5.0 and earlier allows remote attackers to inject arbitrary web script or HTML via the tab parameter to (1) index.php, as demonstrated using mixed case and encoded whitespace characters in the tag; or (2) clientinfo.php, (3) invoices.php, (4) smartlinks.php, and (5) todo.php, as demonstrated using a META tag.