last key wins is terrible advice and has serious security implications. see https://bishopfox.com/blog/json-interoperability-vulnerabilities https://bishopfox.

last key wins is terrible advice and has serious security implications. see https://bishopfox.com/blog/json-interoperability-vulnerabilities https://bishopfox.com/blog/json-interoperability-vulnerabili... or https://www.cvedetails.com/cve/CVE-2017-12635/ https://www.cvedetails.com/cve/CVE-2017-12635/ for concrete examples where this treatment causes security issues. the https://datatracker.ietf.org/doc/html/rfc7493 https://datatracker.ietf.org/doc/html/rfc7493 defines a more strict format where duplicate keys are not allowed.