bug-of-the-month club: n.

[from “book-of-the-month club”, a time-honored mail-order-marketing technique in the U.S.] A mythical club which users of sendmail(8) (the Unix mail daemon) belong to; this was coined on the Usenet newsgroup at a time when sendmail security holes, which allowed outside crackers access to the system, were being uncovered at an alarming rate, forcing sysadmins to update very often. Also, more completely, fatal security bug-of-the-month club. See also kernel-of-the-week club.