Mark the Lyrics

Recon

We are presented with a lyrics website featuring an embedded YouTube video.

Upon examining the source code, we notice that certain characters are wrapped within <mark> HTML elements.

<mark>V</mark>erse <mark>1</mark>: Sơn Tùng M-<mark>T</mark>

The first marked characters are V1T, which suggests that the flag is composed of all the characters contained within the <mark> elements in the DOM.

Exploitation

We can extract all the text contained within the <mark> elements using the browser’s developer tools and a simple JavaScript snippet:

const marks = document.getElementsByTagName("mark");
let flag = "";

for (mark of marks) {
  flag += mark.innerText;
}

console.log(flag);

Flag capture

After running the script, you will see the flag displayed in the console:

Flag: V1T{MCK-pap-cool-ooh-yeah}