Submit a form to szymsza.com which redirects to szymsza.eu

<form action="https://szymsza.com/exploit/redirect.php?form" method="POST">
    <input type="submit" id="btn" value="Submit form">
</form>

Send a fetch to szymsza.com which redirects to szymsza.eu
<br>
<button onclick="f()">Send fetch</button>
<br><br>
<a href="https://szymsza.eu/exploit/origin_log.txt">Inspect the log</a>

<script>
const f = () => fetch("https://szymsza.com/exploit/redirect.php?fetch", {
	method: "POST",
}).finally(() => alert("Sent, check the log"))
</script>