PL/SQL module 3.0.9.8.2 in Oracle 9i Application Server 1.0.2.x allows remote attackers to bypass authentication for a Database Access Descriptor (DAD) by modifying the URL to reference an alternate DAD that already has valid credentials.
http://www.nextgenss.com/papers/hpoas.pdf
http://www.kb.cert.org/vuls/id/193523
http://www.cert.org/advisories/CA-2002-08.html
http://otn.oracle.com/deploy/security/pdf/ias_modplsql_alert.pdf