kioslave/http/http.cpp in KIO in kdelibs 4.10.3 and earlier allows attackers to discover credentials via a crafted request that triggers an "internal server error," which includes the username and password in an error message.
https://bugzilla.redhat.com/show_bug.cgi?id=961981
https://bugs.kde.org/show_bug.cgi?id=319428
http://xorl.wordpress.com/2013/05/22/cve-2013-2074-kde-kdelibs-password-exposure/
http://www.openwall.com/lists/oss-security/2013/05/11/2
http://www.openwall.com/lists/oss-security/2013/05/10/4