[pysaml2] PySAML2 XML external entity attack

PySAML2 allows remote attackers to conduct XML external entity (XXE) attacks via a crafted SAML XML request or response.

References

• https://nvd.nist.gov/vuln/detail/CVE-2016-10127
• https://github.com/rohe/pysaml2/issues/366
• https://github.com/rohe/pysaml2/pull/379
• https://github.com/rohe/pysaml2/commit/6e09a25d9b4b7aa7a506853210a9a14100b8bc9b
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=850716
• http://www.openwall.com/lists/oss-security/2017/01/19/5
• https://github.com/advisories/GHSA-m269-wj6g-c459