This is a very simple “warmup” challenge. The HTML file that is provided contains code that checks for the password:
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var rotFlag = flag.replace(/[a-zA-Z]/g, function(c){return String.fromCharCode((c <= "Z" ? 90 : 122) >= (c = c.charCodeAt(0) + 13) ? c : c - 26);});
if ("PyvragFvqrYbtvafNerRnfl@syner-ba.pbz" == rotFlag) {
alert("Correct flag!");
} else {
...
The source itself hints at ROT encoding, and a site like http://www.rot13.com/ instantly gives us the flag: ClientSideLoginsAreEasy@flare-on.com
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