The Hotblocks module 6.x-1.x before 6.x-1.8 for Drupal allows remote authenticated users with the "administer hotblocks" permission to cause a denial of service (infinite loop and time out) via a block that references itself.
http://www.openwall.com/lists/oss-security/2012/10/07/1
http://www.openwall.com/lists/oss-security/2012/10/04/6