Pymatgen (Python Materials Genomics) is an open-source Python library for materials analysis. A critical security vulnerability exists in the `JonesFaithfulTransformation.from_transformation_str()` method within the `pymatgen` library prior to version 2024.2.20. This method insecurely utilizes `eval()` for processing input, enabling execution of arbitrary code when parsing untrusted input. Version 2024.2.20 fixes this issue.