SECURITY UPDATE: pre-authentication remote code execution in the printing
subsystem via unescaped %J substitution in 'print command'. The
client-controlled job name was passed to the shell with only a single
quote -> underscore transformation, allowing shell metacharacters to
inject arbitrary commands when 'printing' is set to a non-CUPS backend
(sysv, lprng, bsd, plp, aix, hpux, qnx, softq).