The Protected Node module 6.x-1.x before 6.x-1.6 for Drupal does not properly "protect node access when nodes are accessed outside of the standard node view," which allows remote attackers to bypass intended access restrictions.
https://exchange.xforce.ibmcloud.com/vulnerabilities/76291
http://www.securityfocus.com/bid/54001
http://www.openwall.com/lists/oss-security/2012/06/14/3
http://secunia.com/advisories/49509