Exclude Posts Category from Recent Posts Widget

Hi,

I need to exclude a certain category of posts from my recent posts widget. This certain category is only used in Wooslider and its content is not relevant for my posts(news) page or recent posts widget.

I managed to exclude the posts from my posts-page by using the code:

function exclude_category($query) {
if ( $query->is_home() ) {
$query->set('cat', '-xx');
}
return $query;
}
add_filter('pre_get_posts', 'exclude_category');

Yet I am unable to find the right code to do something similar for my recent posts widget.

Could anyone offer some insight? Thanks!