In OpenBSD 6.6, local users can use the su -L option to achieve any login class (often excluding root) because there is a logic error in the main function in su/su.c.
https://www.openwall.com/lists/oss-security/2019/12/04/5
https://www.openbsd.org/errata66.html
https://seclists.org/bugtraq/2019/Dec/8
http://www.openwall.com/lists/oss-security/2019/12/04/5