PySAML2 allows remote attackers to conduct XML external entity (XXE) attacks via a crafted SAML XML request or response.
https://github.com/rohe/pysaml2/pull/379
https://github.com/rohe/pysaml2/issues/366
https://github.com/rohe/pysaml2/commit/6e09a25d9b4b7aa7a506853210a9a14100b8bc9b
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=850716