The issue was addressed with improved permissions logic. This issue is fixed in macOS Monterey 12.0.1, macOS Big Sur 11.6.1. An unprivileged application may be able to edit NVRAM variables.
Apple Security Advisory 2021-10-26-4 - macOS Big Sur 11.6.1 addresses code execution, integer overflow, out of bounds read, and out of bounds write vulnerabilities.