check_by_ssh in Nagios nagios-plugins 2.4.5 allows arbitrary command execution via ProxyCommand, LocalCommand, and PermitLocalCommand with \${IFS}. This has been categorized both as fixed in e8810de, and as intended behavior.
https://joshua.hu/nagios-hacking-cve-2023-37154
https://github.com/nagios-plugins/nagios-plugins/commit/e8810de21be80148562b7e0168b0a62aeedffde6
https://github.com/monitoring-plugins/monitoring-plugins/security/advisories/GHSA-p3gv-vmpx-hhw4