Versions of the npm CLI prior to 6.13.3 are vulnerable to an Arbitrary File Write. It is possible for packages to create symlinks to files outside of thenode_modules folder through the bin field upon installation. A properly constructed entry in the package.json bin field would allow a package publisher to create a symlink pointing to arbitrary files on a user's system when the package is installed. This behavior is still possible through install scripts. This vulnerability bypasses a user using the --ignore-scripts install option.
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.