In Pallets Jinja before 2.8.1, str.format allows a sandbox escape.
lists.opensuse.org/opensuse-security-announce/2019-05/msg00030.html
lists.opensuse.org/opensuse-security-announce/2019-06/msg00064.html
access.redhat.com/errata/RHSA-2019:1022
access.redhat.com/errata/RHSA-2019:1237
access.redhat.com/errata/RHSA-2019:1260
access.redhat.com/errata/RHSA-2019:3964
access.redhat.com/errata/RHSA-2019:4062
github.com/pallets/jinja/commit/9b53045c34e61013dc8f09b7e52a555fa16bed16
palletsprojects.com/blog/jinja-281-released/
usn.ubuntu.com/4011-1/
usn.ubuntu.com/4011-2/