In SilverStripe assets 4.0, there is broken access control on files.
https://github.com/advisories/GHSA-43jj-2rwc-2m3f
https://www.silverstripe.org/download/security-releases/CVE-2019-14273
https://www.silverstripe.org/download/security-releases/
https://www.silverstripe.org/blog/tag/release