Fix performance issue of parsing big HTML messages by disabling HTML5 parser for these (#7331)

CHANGELOG

@@ -23,6 +23,7 @@ CHANGELOG Roundcube Webmail
 - Fix characters encoding in group rename input after group creation/rename (#7330)
 - Fix bug where some message/rfc822 parts could not be attached on forward (#7323)
 - Make install-jsdeps.sh script working without the 'file' program installed (#7325)
+- Fix performance issue of parsing big HTML messages by disabling HTML5 parser for these (#7331)
 
 RELEASE 1.4.3
 -------------

program/lib/Roundcube/rcube_washtml.php

@@ -595,7 +595,11 @@ class rcube_washtml
         $method       = $this->is_xml ? 'loadXML' : 'loadHTML';
 
         // DOMDocument does not support HTML5, try Masterminds parser if available
-        if (!$this->is_xml && class_exists('Masterminds\HTML5')) {
+        if (!$this->is_xml && class_exists('Masterminds\HTML5')
+            // HTML5 parser is slow with content that contains a lot of tags
+            // disable it for such cases (https://github.com/Masterminds/html5-php/issues/181)
+            && substr_count($html, '<') > 10000
+        ) {
             try {
                 $html5 = new Masterminds\HTML5();
                 $node  = $html5->loadHTML($this->fix_html5($html));