wp-login.php in WordPress 2.0.5 and earlier displays different error messages if a user exists or not, which allows remote attackers to obtain sensitive information and facilitates brute force attacks.
https://exchange.xforce.ibmcloud.com/vulnerabilities/31262
http://www.vupen.com/english/advisories/2007/0062
http://www.securityfocus.com/archive/1/455927/100/0/threaded
http://securityreason.com/securityalert/2113
http://security.gentoo.org/glsa/glsa-200701-10.xml
http://secunia.com/advisories/23741