using html as shortcode attribute

I have created a shortcode that retrives and displays top recommended posts based on a meta_key. There are different attributes, which all work, except for once where the content of the attribute is HTML.

Complete code is:

function dot_irt_top_posts ( $atts ) {

// get our variable from $atts
extract(shortcode_atts(array(
    'before' => '<li>',
    'after' => '</li>',
    'number' => '10',
    'post_type' => 'post',
    'year' => '',
    'monthnum' => '',
    'show_count' => '1',
), $atts));

global $wpdb;

$request = "SELECT * FROM $wpdb->posts, $wpdb->postmeta";
$request .= " WHERE $wpdb->posts.ID = $wpdb->postmeta.post_id";

if ($year != '') {
    $request .= " AND YEAR(post_date) = '$year'";
}

if ($monthnum != '') {
    $request .= " AND MONTH(post_date) = '$monthnum'";
}

$request .= " AND post_status="publish" AND post_type="$post_type" AND meta_key='_recommended'";
$request .= " ORDER BY $wpdb->postmeta.meta_value+0 DESC LIMIT $number";
$posts = $wpdb->get_results($request);

$return = '';


foreach ($posts as $item) {
    $post_title = stripslashes($item->post_title);
    $permalink = get_permalink($item->ID);
    $post_count = $item->meta_value;

    $return .= $before;
    $return .= '<a href="' . $permalink . '" title="' . $post_title.'" rel="nofollow">' . $post_title . '</a> ';

    if ( $show_count == '1') {
        $return .= '<span class="votes">' . $post_count . '</span> ';
    }

    //$return .= get_the_post_thumbnail($item->ID, 'showcase-thumbnail');
    $return .= $after;

}
return '<div class="top_10_posts">' . $return . '</div>';

 }
 add_shortcode('irt_top_posts','dot_irt_top_posts');

Now if I use a shortcode as below, the data is returned properly as list.:

 <ul>
     [irt_top_posts post_type="showcase" number="10"]
 </ul>

But if I set ‘before’ & ‘after’ attributes then they are displayed as content instead of being executed as html:

 <div>
     [irt_top_posts post_type="showcase"  before="<div>" after="</div>" number="10"]
 </div>

Do I need some other functions to disable escaping HTML?

Pass just the element names and convert them to tags in your shortcode:

[irt_top_posts post_type="showcase"  container="div" number="10"]

In your callback:

$return "<$container>$return</$container>";