Nagios Core 4.4.2 has XSS via the alert summary reports of plugin results, as demonstrated by a SCRIPT element delivered by a modified check_load plugin to NRPE.
https://lists.debian.org/debian-lts-announce/2018/12/msg00014.html
https://herolab.usd.de/wp-content/uploads/sites/4/2018/12/usd20180026.txt
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00022.html
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00014.html