tj-actions/branch-names is a Github actions repository that contains workflows to retrieve branch or tag names with support for all events. In versions 8.2.1 and below, a critical vulnerability has been identified in the tj-actions/branch-names' GitHub Action workflow which allows arbitrary command execution in downstream workflows. This issue arises due to inconsistent input sanitization and unescaped output, enabling malicious actors to exploit specially crafted branch names or tags. While internal sanitization mechanisms have been implemented, the action outputs remain vulnerable, exposing consuming workflows to significant security risks. This is fixed in version 9.0.0