How to find where an image is used by it’s url

 function searchstring_wpdb(){
    global $wpdb;
    $mytables=$wpdb->get_results("SHOW TABLES");    
    $ss="cdn.cloudflare.com"; //string to search
    $used_is="";
    foreach ($mytables as $mytable)
    {
        foreach ($mytable as $table) 
        {
            $existing_columns = $wpdb->get_col("DESC {$table}", 0);
            foreach ($existing_columns as $existing_column) 
            {
                $last_link =$wpdb->get_results($wpdb->prepare("SELECT * FROM ".$table." WHERE ".$existing_column." LIKE %s", '%'.$ss.'%'));
                if ($last_link){
                    foreach ($last_link as $row) {
                        if (strstr($table,'postmeta')){ 
                            $used_is .= ', Used in post meta:  ' . $row->post_id;
                        } else if (strstr($table,'posts')) {        
                            $used_is .= ',  Used in post types:  ' . $row->ID;
                        } else {
                            $used_is .= ', In Plugin(Table Name): ' . $table . ' And Row ID: '.$row->post_id.$row->ID.$row->id.'<br>';
                            $check_used = $used_is;
                        }
                    }   
                }
            }       
        }
    }
    echo $used_is; // return all post id's where the string is used
}
add_shortcode('show_results', 'searchstring_wpdb');

The above mentioned code will find the string in all wordpress tables, then get the posts id where the string is used. Hope this can help you.
Paste the code in theme functions.php file use shortcode on a page to get all posts id’s or table row id’s having the string cd.clouflare.com