The default configuration of the PL/SQL Gateway web administration interface in Oracle 9i Application Server 1.0.2.x uses null authentication, which allows remote attackers to gain privileges and modify DAD settings.
http://www.securityfocus.com/bid/4292
http://www.nextgenss.com/papers/hpoas.pdf
http://www.kb.cert.org/vuls/id/611776
http://www.cert.org/advisories/CA-2002-08.html
http://otn.oracle.com/deploy/security/pdf/ias_modplsql_alert.pdf