You can protect yourself using existing tools, but it's not trivial and requires serious custom work. Effectively you want minimal permissions and loud failures.

This is something I'm trying to polish for my system now, but the idea is: yarn (and bundler and others) needs to talk only to the repositories. That means yarn install is only allowed outbound connections to localhost running a proxy for packages. It can only write in tmp, its caches, and the current project's node_packages. It cannot read home files beyond specified ones (like .yarnrc). The alias to yarn strips the cloud credentials. All tokens used for installation are read-only. Then you have to do the same for the projects themselves.

On Linux, selinux can do this. On Mac, you have to fight a long battle with sandbox-exec, but it's kinda maybe working. (If it gained "allow exec with specified profile", it would be so much better)

But you may have guessed from the description so far - it's all very environment dependent, time sink-y, and often annoying. It will explode on issues though - try to touch ~/.aws/credentials for example and yarn will get killed and reported - which is exactly what we want.

But internally? The whole environment would have to be redone from scratch. Right now package installation will run any code it wants. It will compile extensions with gyp which is another way of custom code running. The whole system relies on arbitrary code execution and hopes it's secure. (It will never be) Capabilities are a fun idea, but would have to be seriously improved and scoped to work here.

Why yarn instead of pnpm?