The HTTP Strict Transport Security (HSTS) module 6.x-1.x before 6.x-1.1 and 7.x-1.x before 7.x-1.2 for Drupal does not properly implement the "include subdomains" directive, which causes the HSTS policy to not be applied to subdomains and allows man-in-the-middle attackers to have unspecified impact via unknown vectors.
https://www.drupal.org/node/2507563
https://www.drupal.org/node/2507543
https://www.drupal.org/node/2507539
http://www.securitytracker.com/id/1037633