User level separation, while it has improved over the years, was not originally designed assuming unprivileged users were malicious, and even today privilege es

User level separation, while it has improved over the years, was not originally designed assuming unprivileged users were malicious, and even today privilege escalation bugs regularly pop up. If you are going to use it as a sandboxing mechanism, you should at least ensure the sandboxed user doesn't have access to any suid binaries as these regularly have exploits found in them.