OneLogin Ruby-SAML 1.6.0 and earlier may incorrectly utilize the results of XML DOM traversal and canonicalization APIs in such a way that an attacker may be able to manipulate the SAML data without invalidating the cryptographic signature, allowing the attack to potentially bypass authentication to SAML service providers.
https://github.com/advisories/GHSA-x2fr-v8wf-8wwv
https://www.kb.cert.org/vuls/id/475445
https://euvd.enisa.europa.eu/vulnerability/EUVD-2019-0609
https://duo.com/blog/duo-finds-saml-vulnerabilities-affecting-multiple-implementations