Before WordPress 4.9.5, the URL validator assumed URLs with the hostname localhost were on the same host as the WordPress server.
{ "versions": [ { "introduced": "0" }, { "fixed": "4.9.5" } ] }
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2018-10101.json"
[ { "events": [ { "introduced": "0" }, { "last_affected": "8.0" } ] }, { "events": [ { "introduced": "0" }, { "last_affected": "9.0" } ] } ]