Bugzilla 2.17.x, 2.18 before 2.18.2, 2.19.x, and 2.20 before 2.20rc1 inserts a bug into the database before it is marked private, which introduces a race condition and allows attackers to access information about the bug via buglist.cgi before MySQL replication is complete.
https://bugzilla.mozilla.org/show_bug.cgi?id=293159