MantisBT before 1.2.18 allows remote authenticated users to bypass the $g_download_attachments_threshold and $g_view_attachments_threshold restrictions and read attachments for private projects by leveraging access to a project that does not restrict access to attachments and a request to the download URL.
Category : Permissions, Privileges, and Access Controls Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.