Sun Java System Identity Manager (IdM) 7.0 through 8.0 responds differently to failed use of the Forgot Password feature depending on whether the user account exists, which allows remote attackers to enumerate valid usernames.
blogs.sun.com/security/entry/sun_alert_253267_sun_java
secunia.com/advisories/34380
securitytracker.com/id?1021881
sunsolve.sun.com/search/document.do?assetkey=1-21-140936-01-1
sunsolve.sun.com/search/document.do?assetkey=1-66-253267-1
www.securityfocus.com/bid/34191
www.vupen.com/english/advisories/2009/0797