Unaffected query within shortcode

add_shortcode('find_my_special_posts', 'find_my_special_posts');

function find_my_special_posts() {
    $posts = new WP_Query(array(
        'posts_per_page' => -1,
        'post_type' => 'post',
        'tax_query' => array(array(
            'taxonomy' => 'category',
            'field' => 'slug',
            'terms' => 'random-post-term'
        ))
    ));

    $output = '';

    while ($posts->have_posts()) {
        $posts->the_post();
        $output .= '<p>' . get_the_title() . '</p>';
    }

    wp_reset_postdata();

    return empty($output) ? "<p> Sorry matey but you're out of luck. </p>" : $output;
}