Fix handling of some conditional comment tags in HTML message (#1489004)

CHANGELOG

@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix handling of some conditional comment tags in HTML message (#1489004)
 - Add rel="noreferrer" for links in displayed messages (#1484686)
 - Fix so forward as attachment works if additional attachment is added by message_compose hook (#1489000)
 - Add ability to toggle between HTML and text while viewing a message (#1486939)

program/lib/Roundcube/rcube_washtml.php

@@ -413,7 +413,8 @@ class rcube_washtml
 
         // Remove invalid HTML comments (#1487759)
         // Don't remove valid conditional comments
-        $html = preg_replace('/<!--[^->[\n]*>/', '', $html);
+        // Don't remove MSOutlook (<!-->) conditional comments (#1489004)
+        $html = preg_replace('/<!--[^->\[\n]+>/', '', $html);
 
         // turn relative into absolute urls
         $html = self::resolve_base($html);