Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.1, "TaskAttachment.ReadOne()" queries attachments by ID only ("WHERE id = ?"), ignoring the task ID from the URL path. The permission check in "CanRead()" validates access to the task specified in the URL, but "ReadOne()" loads a different attachment that may belong to a task in another project. This allows any authenticated user to download or delete any attachment in the system by providing their own accessible task ID with a target attachment ID. Attachment IDs are sequential integers, making enumeration trivial. Version 2.2.1 patches the issue.