Better escape open graph <meta> strings

system/application/views/arbors/html/wrapper.php

@@ -41,8 +41,8 @@
 <? if (!$book->display_in_index || $is_new || !empty($version_datetime)): ?>
 <meta name="robots" content="noindex, nofollow">
 <? endif ?>
-<meta property="og:title" content="<?=((isset($book))?$book->title.': ':'').((isset($page->version_index))?$title:'Untitled')?>" />
-<meta property="og:site_name" content="<? if (isset($book)) { echo $book->title.((!empty($book->subtitle))?': '.$book->subtitle:''); } ?>" />
+<meta property="og:title" content="<?=((isset($book))?trim(strip_tags($book->title)).': ':'').((isset($page->version_index))?strip_tags($title):'Untitled')?>" />
+<meta property="og:site_name" content="<? if (isset($book)) { echo trim(strip_tags($book->title)).((!empty($book->subtitle))?': '.strip_tags($book->subtitle):''); } ?>" />
 <meta property="og:url" content="<? echo confirm_slash($base_uri).((isset($page->version_index))?$page->slug:''); ?>" />
 <meta property="og:description" content="<? if (isset($page->version_index)) {echo create_excerpt($page->versions[$page->version_index]->content, 34);} else {echo strip_tags($description);} ?>" />
 <meta property="og:image" content="<?=$app_root?>views/arbors/html5_RDFa/scalar_logo_300x300.png" />