WordPress doesn't allow 0.0.0.0/8 in some contexts, as an attempt to block some types of SSRF: https://github.com/WordPress/WordPress/blob/abcbee954f4d8baa5aff

WordPress doesn't allow 0.0.0.0/8 in some contexts, as an attempt to block some types of SSRF: https://github.com/WordPress/WordPress/blob/abcbee954f4d8baa5aff2df566a942c1b48ca2d7/wp-includes/http.php#L563 https://github.com/WordPress/WordPress/blob/abcbee954f4d8baa... If allocations in 0.0.0.0/8 happen someday, users will probably see similar misfeatures in many applications.