In WordPress before 4.9.9 and 5.x before 5.0.1, authors could bypass intended restrictions on post types via crafted input.

References

• advisory http://www.securityfocus.com/bid/106220
• advisory https://codex.wordpress.org/Version_4.9.9
• advisory https://lists.debian.org/debian-lts-announce/2019/02/msg00019.html
• advisory https://wordpress.org/news/2018/12/wordpress-5-0-1-security-release/
• advisory https://wordpress.org/support/wordpress-version/version-5-0-1/
• advisory https://wpvulndb.com/vulnerabilities/9170
• advisory https://www.debian.org/security/2019/dsa-4401
• advisory https://www.zdnet.com/article/wordpress-plugs-bug-that-led-to-google-indexing-some-user-passwords/