In WordPress before 5.2.3, validation and sanitization of a URL in wp_validate_redirect in wp-includes/pluggable.php could lead to an open redirect if a provided URL path does not start with a forward slash.
core.trac.wordpress.org/changeset/45971
github.com/WordPress/WordPress/commit/c86ee39ff4c1a79b93c967eb88522f5c09614a28
lists.debian.org/debian-lts-announce/2019/10/msg00023.html
seclists.org/bugtraq/2020/Jan/8
wordpress.org/news/2019/09/wordpress-5-2-3-security-and-maintenance-release/
wpvulndb.com/vulnerabilities/9863
www.debian.org/security/2020/dsa-4599
www.debian.org/security/2020/dsa-4677