Description
Copier is a library and CLI app for rendering project templates. In versions 9.5.0 through 9.15.1, the `trust` setting's prefix match (`copier/_settings.py`) compares the template URL against a trusted prefix with a raw `str.startswith` and no path normalization, while the URL is normalized when the template is actually fetched (`Path.resolve()` for local paths; libcurl dot-segment removal for `https`). A template reference that textually starts with a trusted prefix but contains `..` is therefore granted trust yet resolves to a different, attacker-controlled template, whose `tasks` / `migrations` / `jinja_extensions` then run without the `--trust` prompt — arbitrary command execution. Version 9.15.2 patches the issue.
Problem types
CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-94: Improper Control of Generation of Code ('Code Injection')
Product status
References
github.com/...copier/security/advisories/GHSA-9gmc-jqmh-3rvm
github.com/...copier/security/advisories/GHSA-9gmc-jqmh-3rvm
github.com/copier-org/copier/releases/tag/v9.15.2