[jwilk]

Restricted mode provides hardly any protection against untrusted code.

Also, it's a bashism. It's not implemented by the OpenBSD's /bin/sh.

[fao_]

openBSD uses mksh which includes a restricted mode (http://www.mirbsd.org/htman/i386/man1/mksh.htm)

[jwilk]

Oh? https://man.openbsd.org/sh.1 doesn't mention -r.

[adamrt]

OpenBSD started out as pdksh I believe, not mksh. But it still has a restricted mode.

https://man.openbsd.org/ksh.1#AUTHORS