Allow plus sign during registration

/** Use below filter to allow plus sign during registration **/

function allow_plus_sign($username, $raw_username, $strict) {
    $new_username = strip_tags($raw_username);
    // Kill octets
    $new_username = preg_replace('|%([a-fA-F0-9][a-fA-F0-9])|', '', $new_username);
    $new_username = preg_replace('/&.?;/', '', $new_username); // Kill entities

   // If strict, reduce to ASCII for max portability.
   if ( $strict )
        $new_username = preg_replace('|[^a-z0-9 _.\-@+]|i', '', $new_username);

    return $new_username;
}
add_filter( 'sanitize_user', 'allow_plus_sign', 10, 3);
add_action( 'wpuf_after_register', 'allow_plus_sign', 10, 3 );