diff --git a/src/wp-includes/html-api/class-wp-html-processor.php b/src/wp-includes/html-api/class-wp-html-processor.php
index cb581fac3988f..bca44cbb670ea 100644
--- a/src/wp-includes/html-api/class-wp-html-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-processor.php
@@ -256,6 +256,16 @@ class WP_HTML_Processor extends WP_HTML_Tag_Processor {
 	 */
 	private $context_node = null;
 
+	/**
+	 * @var WP_HTML_Token[]
+	 */
+	private $after_body_comments = array();
+
+	/**
+	 * @var WP_HTML_Token[]
+	 */
+	private $after_after_body_comments = array();
+
 	/*
 	 * Public Interface Functions
 	 */
@@ -639,12 +649,34 @@ public function next_token(): bool {
 		// Process the next event on the queue.
 		$this->current_element = array_shift( $this->element_queue );
 		if ( ! isset( $this->current_element ) ) {
-			// There are no tokens left, so close all remaining open elements.
+			// The document has been fully processed. Perform final actions.
+
+			// Close out the body:
+			if ( $this->state->stack_of_open_elements->contains( 'BODY' ) ) {
+				$this->state->stack_of_open_elements->pop_until( 'BODY' );
+			}
+
+			// Deal with after body comments:
+			foreach ( $this->after_body_comments as $token ) {
+				$this->insert_html_element( $token );
+			}
+			$this->after_body_comments = array();
+
+			// Close out everything on the stack of open elements:
 			while ( $this->state->stack_of_open_elements->pop() ) {
 				continue;
 			}
+			// Deal with after after body comments:
+			foreach ( $this->after_after_body_comments as $token ) {
+				$this->insert_html_element( $token );
+			}
+			$this->after_after_body_comments = array();
 
-			return empty( $this->element_queue ) ? false : $this->next_token();
+			if ( ! empty( $this->element_queue ) ) {
+				return $this->next_token();
+			}
+
+			return false;
 		}
 
 		$is_pop = WP_HTML_Stack_Event::POP === $this->current_element->operation;
@@ -868,6 +900,9 @@ public function step( $node_to_process = self::PROCESS_NEXT_NODE ): bool {
 				$this->has_self_closing_flag(),
 				$this->release_internal_bookmark_on_destruct
 			);
+			if ( '#comment' === $token_name ) {
+				$this->state->current_token->comment_type = $this->get_comment_type();
+			}
 		}
 
 		$parse_in_current_insertion_mode = (
@@ -3964,8 +3999,8 @@ private function step_after_body(): bool {
 			case '#comment':
 			case '#funky-comment':
 			case '#presumptuous-tag':
-				$this->bail( 'Content outside of BODY is unsupported.' );
-				break;
+				$this->after_body_comments[] = $this->state->current_token;
+				return $this->step();
 
 			/*
 			 * > A DOCTYPE token
@@ -4040,7 +4075,7 @@ private function step_in_frameset(): bool {
 				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
 					return $this->step_in_body();
 				}
-				$this->bail( 'Non-whitespace characters cannot be handled in frameset.' );
+				goto in_frameset_anything_else;
 				break;
 
 			/*
@@ -4120,6 +4155,7 @@ private function step_in_frameset(): bool {
 				return $this->step_in_head();
 		}
 
+		in_frameset_anything_else:
 		// Parse error: ignore the token.
 		return $this->step();
 	}
@@ -4159,7 +4195,7 @@ private function step_after_frameset(): bool {
 				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
 					return $this->step_in_body();
 				}
-				$this->bail( 'Non-whitespace characters cannot be handled in after frameset' );
+				goto after_frameset_anything_else;
 				break;
 
 			/*
@@ -4198,6 +4234,7 @@ private function step_after_frameset(): bool {
 				return $this->step_in_head();
 		}
 
+		after_frameset_anything_else:
 		// Parse error: ignore the token.
 		return $this->step();
 	}
@@ -4230,8 +4267,8 @@ private function step_after_after_body(): bool {
 			case '#comment':
 			case '#funky-comment':
 			case '#presumptuous-tag':
-				$this->bail( 'Content outside of HTML is unsupported.' );
-				break;
+				$this->after_after_body_comments[] = $this->state->current_token;
+				return $this->step();
 
 			/*
 			 * > A DOCTYPE token
@@ -4293,8 +4330,8 @@ private function step_after_after_frameset(): bool {
 			case '#comment':
 			case '#funky-comment':
 			case '#presumptuous-tag':
-				$this->bail( 'Content outside of HTML is unsupported.' );
-				break;
+				$this->insert_html_element( $this->state->current_token );
+				return true;
 
 			/*
 			 * > A DOCTYPE token
@@ -4319,7 +4356,7 @@ private function step_after_after_frameset(): bool {
 				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
 					return $this->step_in_body();
 				}
-				$this->bail( 'Non-whitespace characters cannot be handled in after after frameset.' );
+				goto after_after_frameset_anything_else;
 				break;
 
 			/*
@@ -4329,6 +4366,7 @@ private function step_after_after_frameset(): bool {
 				return $this->step_in_head();
 		}
 
+		after_after_frameset_anything_else:
 		// Parse error: ignore the token.
 		return $this->step();
 	}
diff --git a/src/wp-includes/html-api/class-wp-html-token.php b/src/wp-includes/html-api/class-wp-html-token.php
index d5e51ac29007f..4bfa9eb9e6ada 100644
--- a/src/wp-includes/html-api/class-wp-html-token.php
+++ b/src/wp-includes/html-api/class-wp-html-token.php
@@ -46,6 +46,17 @@ class WP_HTML_Token {
 	 */
 	public $node_name = null;
 
+	/**
+	 * Comment type
+	 *
+	 * @since 6.7.0
+	 *
+	 * @see WP_HTML_Processor::get_comment_type()
+	 *
+	 * @var string|null
+	 */
+	public $comment_type = null;
+
 	/**
 	 * Whether node contains the self-closing flag.
 	 *
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorHtml5lib.php b/tests/phpunit/tests/html-api/wpHtmlProcessorHtml5lib.php
index 54d60f8c78a66..5267f537ac778 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessorHtml5lib.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorHtml5lib.php
@@ -33,6 +33,8 @@ class Tests_HtmlApi_Html5lib extends WP_UnitTestCase {
 		'tests14/line0055'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
 		'tests19/line0488'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
 		'tests19/line0500'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
+		'tests19/line0488'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
+		'tests19/line0500'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
 		'tests19/line1079'       => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
 		'tests2/line0207'        => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',
 		'tests2/line0686'        => 'Unimplemented: This parser does not add missing attributes to existing HTML or BODY tags.',