Fix bug where HTML messages with invalid/excessive css styles couldn't be displayed (#1490539)

Technically speaking we remove the whole CSS content when it has more than 5k lines.

CHANGELOG

@@ -6,6 +6,7 @@ CHANGELOG Roundcube Webmail
 - Fix so database_attachments::cleanup() does not remove attachments from other sessions (#1490542)
 - Fix responses list update issue after response name change (#1490555)
 - Fix bug where message preview was unintentionally reset on check-recent action (#1490563)
+- Fix bug where HTML messages with invalid/excessive css styles couldn't be displayed (#1490539)
 
 RELEASE 1.1.3
 -------------

program/steps/mail/func.inc

@@ -948,6 +948,13 @@ function rcmail_washtml_callback($tagname, $attrib, $content, $washtml)
         break;
 
     case 'style':
+        // Crazy big styles may freeze the browser (#1490539)
+        // remove content with more than 5k lines
+        if (substr_count($content, "\n") > 5000) {
+            $out = '';
+            break;
+        }
+
         // decode all escaped entities and reduce to ascii strings
         $stripped = preg_replace('/[^a-zA-Z\(:;]/', '', rcube_utils::xss_entity_decode($content));