Emilio José Calvo Carrasco on "[Plugin: Wordfence Security] W3C validation fix"

Sorry, this is the correct fix of line 1288:
$URL .= '?action=wordfence_logHuman&amp ;hid=' . wfUtils::encrypt(self::$hitID);

VERY IMPORTANT: without space on '&amp ;' - WordPress.org change the code to '&'. Sorry :-(.