The Menu module does not correctly handle certain user input when displaying the menu administration overview. Users privileged to create new menus can insert arbitrary HTML and script code into the menu module administration page. Such a cross-site scripting attack may lead to the malicious user gaining administrative access. Wikipedia has more information about cross-site scripting (XSS).
This issue affects Drupal 6.x only.
Vendor Status:
Drupal issued an update for this vulnerability