Adenion Blog2Social plugin for WordPress before 9.1.0 allows low-privileged users to enumerate WordPress user accounts. The b2s_get_select_mandant_user AJAX handler in includes/Ajax/Get.php resolves arbitrary user IDs supplied in the owner parameter to display names without verifying that the caller is authorized to read user account data, allowing any user with the edit_posts capability to map WordPress user IDs to display names and confirm account existence for arbitrary IDs.