请教ctf web 问题

ctf web 问题

  
    highlight_file(__FILE__);
    error_reporting(0); 
    ini_set('open_basedir',"/var/www/html");
    $file=$_GET['f'];
    if(preg_match("/flag|secret|index/i",$file))
    {
      die("nononono");
    }
    include_once($file);
    $sec=$_GET['pop'];
    if(isset($sec))
    {
       unserialize($sec);
    }    
?>

我绕不过去，请帮帮忙

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