Cómo excluir categoría en enlace aleatorio de entrada única

add_action('init','random_post');function random_post() {
       global $wp;
       $wp->add_query_var('random');
       add_rewrite_rule('random/?$', 'index.php?random=1', 'top');
}
 
add_action('template_redirect','random_template');
function random_template() {
       if (get_query_var('random') == 1) {
               $posts = get_posts('post_type=post&orderby=rand&numberposts=1');
               foreach($posts as $post) {
                       $link = get_permalink($post);
               }
               wp_redirect($link,307);
               exit;
       }
}

               $posts = get_posts('post_type=post&orderby=rand&numberposts=1&category=-1');

$posts = get_posts('post_type=post&orderby=rand&numberposts=1&category=-6');

add_action('init','random_post');
function random_post() {
       global $wp;
       $wp->add_query_var('random');
       add_rewrite_rule('random/?$', 'index.php?random=1', 'top');
}
 
add_action('template_redirect','random_template');
function random_template() {
       if (get_query_var('random') == 1) {
               $posts = get_posts('post_type=video&orderby=rand&numberposts=1');
               foreach($posts as $post) {
                       $link = get_permalink($post);
               }
               wp_redirect($link,307);
               exit;
       }
}

<!-- empieza bloque aleatorios-->
    <div id="cuadrosidebar">
      <div class="news-b-header">
        <div class="news-b-header-bg">
          <img src="http://3.bp.blogspot.com/-_wheyWnfkCY/U4SHw5vbH7I/AAAAAAAAGKM/K8BMAxwHUP8/s1600/peliculas.png" width="26" height="26" style="float:left;margin-top: 10px;padding-right:15px"/>
          <div class="titlesidebar">
           Películas al azar
          </div>
          <span class="subtitlesidebar">
            Selecciona tu favorita 
          </span>
        </div>
      </div>
      <div class="clear">
      </div>
      <div class="clear">
      </div>
      <div style="width:220px;padding-left: 20px;">
   <table>
     <?php $rand_posts = get_posts('numberposts=5&orderby=rand');
 foreach( $rand_posts as $post ) :
 ?>
    <?php if (!in_category(1)):?>

<div style="padding-top:8px;border-bottom:1px solid #444d6a;color:#fff;">  
<div style="float:left;padding-right:15px;">
<a href="<?php the_permalink() ?>">                  
<?php $url = wp_get_attachment_url( get_post_thumbnail_id($post->ID) );?>        
<img src="<?php echo $url; ?>" width="95px" height="125px" style="border: 2px solid #999;" title="<?php the_title(); ?>"/>                 
</a>
</div>
<div><a style="text-decoration:none;color:#fff;font-weight:bold;font-size:14px" href="<?php the_permalink() ?>"><?php the_title(); ?></a><br/>
<?php the_time('j \d\e\ F \d\e\l\ Y') ?>
<br/><br/><br/><br/><br/><br/><br/><br/><br/></div></div>
           <?php endif; ?>
 
<?php wp_reset_query(); ?>   
 <?php endforeach; ?>
      </table>

  </div>
      <br/>
   
  </div>
    <br/>
    <br/>
<!-- termina bloque aleatorios-->