Is dangerous using ob_start on shortcode??

Hi everyone, I want to make a shortcode for calling a few post from X category. This’s my code :

/*-----------------------------------------------------------------------------------*/
/* Category - shortcode
/*-----------------------------------------------------------------------------------*/
function shortcode_category($atts, $content = null) {
		extract(shortcode_atts(array(
			"categ_id" => '',
			"show" => '3',
			"title" => '',
		), $atts));

		global $wp_query;

		$temp = $wp_query;
		$wp_query = null;
		$wp_query = new WP_Query();

				$query .= '&cat='.$categ_id;

				$query .= '&showposts='.$show;

				$query .= $query;

			$wp_query->query($query);
			ob_start();

?>

	<span class="divider2"><span><?php echo $title; ?></span></span><!--DIVIDER-->
	<div class="row-fluid">
			<div class="content">
				<div class="span12">
					<div class="row-fluid">

<?php while ($wp_query->have_posts()) : $wp_query->the_post(); $do_not_duplicate = $post->ID; ?>

	<div class="span4 recent_blog">
	<div class="recent-img">
									<?php the_post_thumbnail('single_image'); ?>
									<div class="caption">
										<?php if ( has_post_format( 'video' )) {
											?>

<a href="<?php the_permalink(); ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">

<img src="<?php bloginfo('stylesheet_directory'); ?>/img/iconsweet/format-video.png" alt="Video Format" />	

</a>									<?php
	}
										else if ( has_post_format( 'image' )) {
									?>

<a href="<?php the_permalink(); ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">

<img src="<?php bloginfo('stylesheet_directory'); ?>/img/iconsweet/format-images.png" alt="Image Format" />

</a>
									<?php
	}
	?>

</div>
								</div>
<a href="<?php the_permalink(); ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><h4><?php the_title(); ?></h4></a>
<div class="date"><?php the_time("F jS, Y");?> <?php _e('|','');?> <?php comments_number('No Comments', 'One Comment', '% Comments'); ?></div>

<?php wpe_excerpt('wpe_excerptlength_index_sc', ''); ?>	

<div class="mores"><a href="<?php the_permalink(); ?>"><?php _e('More &rarr;','');?> </a></div>	

</div>
<?php endwhile; ?>
<div class="clearfix"></div>

</div>

</div>
<div class="clearfix"></div>
</div>
</div>

	<?php $wp_query = null; $wp_query = $temp;
	$content = ob_get_contents();
	ob_end_clean();
	return $content;  

}

add_shortcode ('categories', 'shortcode_category');

The question is:
my code is secure? or my code contains code that prohibited and dangerous?

Thank you everyone.