Challenge Description#

backup my index pls

Analysis#

Because there was no URL given for the challenge instance, I initially thought the target was the CTFd site itself. The hint “backup my index” strongly suggests a leftover backup file such as .bak, .old, or .swp.

Exploitation#

Access the backup file directly:

1
curl https://ctf.sriwijayasecuritysociety.com/index.php.bak

The response contained the flag directly inside the HTML:

1
<main role="main">
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    <div class="container">
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        <p>SCSC26{4h_1_f0rg3t_to_d3letE}</p>
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    </div>
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</main>