Add the following code to your functions.php file:
/* * Add target blank to content links */ function wp_add_target_blank($content) { // Get the site url $site_url = get_site_url(); // Get all the links in the article preg_match_all('#<a ([^>]*)>#i', $content, $matches); // Loop through each link foreach ($matches[1] as $key=>$value) { // If link does not contain the site_url or the text _blank, add target="_blank" if (!stristr($value, $site_ul) && !stristr($value, '_blank')) { $content = str_replace('<a '.$value.'>', '<a target="_blank" '.$value.'>', $content); } } // Return the modified content return $content; } // Add the wordpress filter add_filter( 'the_content', 'wp_add_target_blank' );