On version 0.2.3 there is a bug in the OpenAdmin > Firewall > Firewall Configuration page when CSF is used, that prevents opening the csf.conf file:
Unable to create csf UI temp file: 'utf-8' codec can't decode byte 0xa9 in position 1422: invalid start byte
This is resolved in the upcoming update scheduled in a few days. The workaround is to run:
wget -O /usr/local/admin/modules/security/csf.pl https://gist.githubusercontent.com/radovanjecmenica/18a13c8a66340bd4ed624bdedb0d9050/raw/a5d6abc1f1d9c867a3d2811cc085ae774b25dad2/csf.pl