OS command injection in SHLOMIF Config::IniFiles

Summary

Config::IniFiles versions before 3.001000 for Perl allow OS command injection and file overwrite via a 2-arg open() of the -file argument in _make_filehandle. Config::IniFiles::_make_filehandle opens a filename argument with Perl's 2-arg open(), so a filename that begins or ends with a pipe ("| cmd", "cmd |") or begins with a redirect ("> path", ">> path") is run as a command or redirect rather than opened as a file. The helper is the open path behind the documented -file argument: new(-file => $thing) reaches it through ReadConfig. An in-memory scalar reference (-file => \$text) does not open a path and is unaffected. Any caller that forwards untrusted input to the -file argument can run an arbitrary command or truncate a file under the process UID.