My patch for ISPConfig 188.8.131.52 also works for the latest version 184.108.40.206.
Only the language file is not patched, but that can be easily realized by hand. Please understand that I do not find the time at the moment to adapt the patch accordingly – but that’s just a visual aspect. After patching the current version, only a few lines need to be inserted into code>nterface/web/admin/lib/lang/en_server_config.lng:
$wb["vhost_rewrite_v6_txt"] = 'Rewrite IPv6 on Mirror';
$wb["v6_prefix_wrong"] = 'Invalid v6 Netmask format.';
$wb["v6_prefix_end"] = 'Prefix - must end with ::';
$wb["v6_prefix_length"] = 'Prefix too long according to defined IPv6 ';