The `nix-nar` crate's `Decoder::unpack` function improperly handles path containment when extracting archive entries, allowing a malicious NAR archive to write files outside the intended destination directory via path traversal. This occurs because symlink targets are not validated and the containment check only compares path strings without considering symlinks created earlier during unpacking. An attacker can craft an archive that creates symlinks pointing outside the destination and then writes files through these symlinks, potentially enabling code execution by placing files in attacker-controlled locations.