shibsp/metadata/DynamicMetadataProvider.cpp in the Dynamic MetadataProvider plugin in Shibboleth Service Provider before 2.6.1 fails to properly configure itself with the MetadataFilter plugins and does not perform critical security checks such as signature verification, enforcement of validity periods, and other checks specific to deployments, aka SSPCPP-763.
https://www.debian.org/security/2017/dsa-4038
https://shibboleth.net/community/advisories/secadv_20171115.txt
https://lists.debian.org/debian-lts-announce/2017/11/msg00025.html