diff --git a/core/modules/filter/src/Plugin/Filter/FilterHtml.php b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
index 345ae193dea9d0c88eb0bd728a89af3d4f513c1c..0718b73092e07f959e20f326deed4c03b187b868 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterHtml.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
@@ -7,6 +7,9 @@
use Drupal\Component\Utility\Html;
use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;
+use Masterminds\HTML5\Parser\DOMTreeBuilder;
+use Masterminds\HTML5\Parser\Scanner;
+use Masterminds\HTML5\Parser\Tokenizer;
/**
* Provides a filter to limit allowed HTML tags.
@@ -258,7 +261,20 @@ public function getHTMLRestrictions() {
$star_protector = '__zqh6vxfbk3cg__';
$html = str_replace('*', $star_protector, $html);
- $dom = Html::load($html);
+ // Use HTML5 parser with a custom tokenizer to correctly parse tags that
+ // normally use text mode, such as iframe.
+ $events = new DOMTreeBuilder(FALSE, ['disable_html_ns' => TRUE]);
+ $scanner = new Scanner('<body>' . $html);
+ $parser = new class($scanner, $events) extends Tokenizer {
+
+ public function setTextMode($textMode, $untilTag = NULL) {
+ // Do nothing, we never enter text mode.
+ }
+
+ };
+ $parser->parse();
+
+ $dom = $events->document();
$xpath = new \DOMXPath($dom);
foreach ($xpath->query('//body//*') as $node) {
$tag = $node->tagName;
diff --git a/core/modules/filter/tests/src/Kernel/FilterKernelTest.php b/core/modules/filter/tests/src/Kernel/FilterKernelTest.php
index 660ba730da9f23b04c6e0c215e6ec85eecccc32b..357437c334462a953a853cadaeb37ede692f11ef 100644
--- a/core/modules/filter/tests/src/Kernel/FilterKernelTest.php
+++ b/core/modules/filter/tests/src/Kernel/FilterKernelTest.php
@@ -579,6 +579,17 @@ public function testHtmlFilter() {
$this->assertNormalized($f, '<a>link</a>', 'HTML filter removes allowed attributes that have a not explicitly allowed value.');
$f = (string) $filter->process('<a href="/beautiful-animals" kitten="cute" llama="epic majestical">link</a>', Language::LANGCODE_NOT_SPECIFIED);
$this->assertSame('<a href="/beautiful-animals" llama="epic majestical">link</a>', $f, 'HTML filter keeps explicitly allowed attributes with an attribute value that is also explicitly allowed.');
+
+ // Allow iframes and check that the subsequent tags are parsed correctly.
+ $filter->setConfiguration([
+ 'settings' => [
+ 'allowed_html' => '<iframe> <a href llama>',
+ 'filter_html_help' => 1,
+ 'filter_html_nofollow' => 0,
+ ],
+ ]);
+ $f = (string) $filter->process('<a kitten="cute" llama="awesome">link</a>', Language::LANGCODE_NOT_SPECIFIED);
+ $this->assertNormalized($f, '<a llama="awesome">link</a>');
}
/**