Yes, but it can be countered by pinning "random-script-from-the-internet.sh" to the untrusted environment. The fork/exec inside bash (or whatever bash is using

Yes, but it can be countered by pinning "random-script-from-the-internet.sh" to the untrusted environment. The fork/exec inside bash (or whatever bash is using now) should take care or that, or the kernel itself which is probably a better option. bash + ls -> trusted because ls is in some way marked as trusted, bash + random-script -> untrusted, possibly by default.