FileGator: Missing authorization in GET /batchdownload allows cross-user retrieval of another user's archive

FileGator is a multi-user file manager. Prior to 7.15.0, GET /batchdownload in backend/Controllers/DownloadController.php uses batchDownloadStart() to stream a shared temporary archive selected by the request-supplied uniqid without checking that the current session created it. In deployments with distinct per-user home directories, a valid user with read, download, and batchdownload permissions who obtains another user's active archive id can cross that boundary and retrieve the victim's batch archive. The archive lifetime and id-acquisition requirement limit exploitation, but a successful replay also deletes the victim's pending archive. This issue is fixed in version 7.15.0.