Outlook conditional comments <![if !vml]> / <![endif]> shown as text in thread body #5676 from il2020/vml-fix

Outlook conditional comments <![if !vml]> / <![endif]> shown as text in thread body

app/Console/Commands/FetchEmails.php

@@ -1598,8 +1598,12 @@ class FetchEmails extends Command
         $body = \Eventy::filter('fetch_emails.separate_reply.preprocess_body', $body ?? '');
 
         if ($is_html) {
+            // Remove Outlook "downlevel-revealed" conditional comments (<![if !vml]>...<![endif]>),
+            // preserving the data inside. Otherwise DOMDocument turns them into escaped text.
+            $body = preg_replace('/<!\[(?:if\s[^\]]*|endif)\]>/i', '', $body) ?: $body;
+
             // Extract body content from HTML
-            
+
             // Proton has it's own unique way of placing replies:
             // https://github.com/freescout-help-desk/freescout/issues/4537#issuecomment-2629836738
             if ($is_reply

app/Thread.php

@@ -329,6 +329,11 @@ class Thread extends Model
         // https://github.com/freescout-helpdesk/freescout/pull/3865#issuecomment-1990758149
         $body = preg_replace('/<!\-\-\[if [^>]+\]><!\-\->(.*?)<![ ]+\-\-<!\[endif\]\-\->/s', '$1', $body);
 
+        // Remove Outlook "downlevel-revealed" conditional comments (<![if !vml]>...<![endif]>),
+        // preserving the data inside. Browsers ignore them, but the purifier escapes them as text.
+        // Emails fetched before the fix have them already escaped (&lt;![if !vml]&gt;) in the DB.
+        $body = preg_replace('/(?:<|&lt;)!\[(?:if\s[^\]]*|endif)\](?:>|&gt;)/i', '', $body) ?: $body;
+
         // https://github.com/freescout-helpdesk/freescout/issues/3894
         // Remove <!--[if !mso]><!--> and <!--<![endif]--> comments, preserving the data inside
         //$body = preg_replace('/(<!\-\-\[if [^>]+\]>|<!\[endif\]\-\->)/', '', $body);