Impact It's possible for an authenticated backoffice-user to enumerate and traverse paths/files on the systems filesystem and read their contents, on Mac/Linux Umbraco installations using Forms. As Umbraco Cloud runs in a Windows environment, Cloud users aren't affected.

Patches This issue affects versions 16 and 17 of Umbraco Forms and is patched in 16.4.1 and 17.1.1

Workarounds If upgrading is not immediately possible, users can mitigate this vulnerability by: Configuring a WAF or reverse proxy to block requests containing path traversal sequences (../, ..\) in the fileName parameter of the export endpoint Restricting network access to the Umbraco backoffice to trusted IP ranges Blocking the /umbraco/forms/api/v1/export endpoint entirely if the export feature is not required

However, upgrading to the patched version is strongly recommended.

References Credit to Kevin Joensen from Baldur Security for finding this vulnerability