drupal: open redirect

The Overlay module in Drupal core displays administrative pages as a
layer over the current page (using JavaScript), rather than replacing
the page in the browser window. The Overlay module does not sufficiently
validate URLs prior to displaying their contents, leading to an open
redirect vulnerability.

This vulnerability is mitigated by the fact that it can only be used
against site users who have the "Access the administrative overlay"
permission, and that the Overlay module must be enabled.