Before version 4.8.2, WordPress was vulnerable to cross-site scripting in oEmbed discovery.
https://www.debian.org/security/2017/dsa-3997
https://wpvulndb.com/vulnerabilities/8913
https://wordpress.org/news/2017/09/wordpress-4-8-2-security-and-maintenance-release/
https://core.trac.wordpress.org/changeset/41448