Security updates for Friday

Security updates have been issued by CentOS (firefox), Debian (cron and ntfs-3g), Fedora (firefox, ghostscript, libzip, python2-django1.11, PyYAML, tcpflow, and xen), Mageia (ansible, firefox, and ImageMagick/GraphicsMagick), Red Hat (ghostscript), Scientific Linux (firefox and ghostscript), SUSE (libxml2, unzip, and wireshark), and Ubuntu (firefox, ghostscript, libsolv, ntfs-3g, p7zip, and snapd).