In WordPress before 4.7.3 (wp-includes/embed.php), there is authenticated Cross-Site Scripting (XSS) in YouTube URL Embeds.
https://wpvulndb.com/vulnerabilities/8768
https://wordpress.org/news/2017/03/wordpress-4-7-3-security-and-maintenance-release/
https://github.com/WordPress/WordPress/commit/419c8d97ce8df7d5004ee0b566bc5e095f0a6ca8
https://codex.wordpress.org/Version_4.7.3
http://www.securitytracker.com/id/1037959