AngstromCTF2019: Control You

The Challenge

Control You Web 20
Only those who give us the flag are exempt from our control.
Author: kmh11
link: https://controlyou.2019.chall.actf.co/

The Solution

Upon inspecting the page, the flag actf{control_u_so_we_can’t_control_you} is readily visible in the page source.

<!DOCTYPE html>
<html>
<head>
    <title>Hypnotization</title>
</head>
<body style="background: url(https://66.media.tumblr.com/15d3f53cb56f04dba66dfd53aed24b7f/tumblr_o87xi4XjVB1twd8ddo1_400.gif);&#34;>
    <div style="text-align: center; position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); color: red; font-family: 'Comic Sans MS', sans-serif;">
        <h1 style="background-color: blue;">Hypnotization in progress…</h1>
        <h2 style="color: green; background-color: yellow;">To stop hypnotization enter the flag below:</h2>
        <input type="password" id="flag" style="font-size: 3em;"><br>
        <button type="button" onclick="stop()" style="background: blue; border: 0.5em solid red; font-size: 2em; font-family: 'Comic Sans MS', sans-serif; margin-top: 1em; cursor: pointer;">Stop Hypnotization</button>
    </div>
    <script>
    function stop() {
        if (flag.value === "actf{control_u_so_we_can't_control_you}") {
            document.body.style.background = "red";
        }
    }
    </script>
</body>
</html>