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Suggestion detail

Untriaged
created 2 months, 3 weeks ago
Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true

Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently write to arbitrary directories outside the destination path by using directory a symlink along with `_preserve_symlinks: true` and a generated directory structure whose rendered path is inside the symlinked directory. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc. Version 9.11.2 patches the issue.

Affected products

copier
  • ==< 9.11.2

Matching in nixpkgs

pkgs.copier

Library and command-line utility for rendering projects templates

pkgs.apksigcopier

Copy/extract/patch android apk signatures & compare APKs

pkgs.gnomeExtensions.copier

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  • nixos-unstable 8
    • nixpkgs-unstable 8
    • nixos-unstable-small 8
  • nixos-25.11 8
    • nixpkgs-25.11-darwin 8

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