The expandArguments function in the database abstraction API in Drupal core 7.x before 7.32 does not properly construct prepared statements, which allows remote attackers to conduct SQL injection attacks via an array containing crafted keys.
https://www.drupal.org/SA-CORE-2014-005
http://www.securityfocus.com/bid/70595
http://www.securityfocus.com/archive/1/533706/100/0/threaded