The oEmbed protocol implementation in WordPress before 4.5.3 allows remote attackers to cause a denial of service via unspecified vectors.
https://wpvulndb.com/vulnerabilities/8523
https://wordpress.org/news/2016/06/wordpress-4-5-3/
https://lists.debian.org/debian-lts-announce/2018/07/msg00046.html
https://codex.wordpress.org/Version_4.5.3