virtualenv is a tool for creating isolated virtual python environments. From 21.14.8 until 21.14.10, the app-data seeder can leave an environment linked to temporary package files that virtualenv deletes when creation finishes. The environment-variable and configuration-file forms of symlink_app_data can enable this state even though the command-line flag is disabled for temporary app-data. The resulting environment depends on a cache pathname that its owner no longer controls. This issue is fixed in version 21.14.10.