SQL injection vulnerability in template-functions-category.php in WordPress 1.5.1 allows remote attackers to execute arbitrary SQL commands via the $cat_ID variable, as demonstrated using the cat parameter to index.php.
http://www.securityfocus.com/bid/13809
http://wordpress.org/development/2005/05/security-update/
http://security.gentoo.org/glsa/glsa-200506-04.xml
http://secunia.com/advisories/15517