In libzypp before 20170803 it was possible to retrieve unsigned packages without a warning to the user which could lead to man in the middle or malicious servers to inject malicious RPM packages into a users system.
https://www.suse.com/de-de/security/cve/CVE-2017-7436/
https://lists.opensuse.org/opensuse-security-announce/2017-08/msg00002.html