You are correct. Linux is a single user OS. Any rogue program can almost certainly escalate privileges using any number of strategies across a vast and complex

You are correct. Linux is a single user OS. Any rogue program can almost certainly escalate privileges using any number of strategies across a vast and complex surface area. It's been almost two decades since unix systems were routinely used in true multi tenancy situations with untrusted tenants. Since then nobody has paid any attention to this aspect of security.