CVE-2026-55471: Improper Restriction of XML External Entity Reference

HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.10, org.hl7.fhir.utilities.XsltUtilities saxonTransform... overloads instantiated a bare net.sf.saxon.TransformerFactoryImpl without ACCESSEXTERNALDTD or ACCESSEXTERNALSTYLESHEET...