Velero vulnerable to file path traversal when extracting from backup's tarball

Velero is an open source tool for backing up, restoring, and migrating Kubernetes cluster resources and persistent volumes. Prior to 1.18.1, an attacker who compromises the backup object-storage backend can upload a malicious backup tarball containing parent-directory paths that escape the extraction directory during restore and overwrite sensitive files in the Velero pod filesystem. This issue is fixed in version 1.18.1.