As an ethical hacker, I am attempting to identify vulnerabilities in a website that utilizes curl to fetch content from localhost on the server. I have experimented with various inputs in the provided input field. Below is the corresponding JavaScript code:

<script>
    $(document).ready(function () {
        $('#fetchForm').submit(function (event) {
            event.preventDefault();
            var url = $('#url').val();
            $.ajax({
                type: 'POST',
                url: '/fetch',
                data: {url: url},
                success: function (response) {
                    $('#contentResult').html('<h2 class="mt-3">Fetched Content</h2><pre>' + response.content + '</pre>');
                },
                error: function (error) {
                    $('#contentResult').html('<div class="alert alert-danger" role="alert">' + error.responseJSON.error + '</div>');
                }
            });
        });
    });
</script>

Do you have any suggestions on how to proceed?