But what they should have is a CDN with their own extensions and verified binaries. This way they can ship new versions of extensions without bumping their editor version.
How many language servers are we talking about here for the average dev? Three?
The only point of this would be if you didn't want to download the language server for untrusted code.
I think what people really want is workspace location permissions...
The real problem is "running" the language server on untrusted code. That's where there should be a confirm dialog.
But it's a separate issue about workspace permissions.
That's the only vulnerability here and it exists on at least one some level in all editors in language servers. (VSCode's workspace permissions aren't that secure)
That strikes me as more of a UX problem. Doing a bunch of sketchy things behind the user's back is absolutely not a solution though.