The awk program string-interpolated the slug
(which embeds the untrusted, mirror-supplied version)
into its source, so a crafted version such as
`v1"==$2){system("touch${IFS}/tmp/x")}#`
was executed by awk's `system()`.
Pass the value via `-v tarball=...` so awk treats it as data and never as code.
See GHSA-3c52-35h2-gfmm
(a second injection sink fed by the same untrusted version field that `nvm_download`'s eval was; the source-install path reaches this during a normal `nvm install <version>`).