The WordPress plugin, Email Subscribers & Newsletters, before 4.2.3 had a flaw that allowed for unauthenticated option creation. In order to exploit this vulnerability, an attacker would need to send a /wp-admin/admin-post.php?es_skip=1&option_name= request.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-19982
• https://wpvulndb.com/vulnerabilities/9946
• https://www.wordfence.com/blog/2019/11/multiple-vulnerabilities-patched-in-email-subscribers-newsletters-plugin/