The data collection script for Bugzilla 2.14.x before 2.14.5, 2.16.x before 2.16.2, and 2.17.x before 2.17.3 sets world-writable permissions for the data/mining directory when it runs, which allows local users to modify or delete the data.
http://www.securityfocus.com/bid/6502
http://www.redhat.com/support/errata/RHSA-2003-012.html
http://www.iss.net/security_center/static/10971.php