diff --git a/src/wp-includes/html-api/class-wp-html-open-elements.php b/src/wp-includes/html-api/class-wp-html-open-elements.php
index fe5625545b0ac..4fb1cc2e8de40 100644
--- a/src/wp-includes/html-api/class-wp-html-open-elements.php
+++ b/src/wp-includes/html-api/class-wp-html-open-elements.php
@@ -37,6 +37,17 @@ class WP_HTML_Open_Elements {
 	 */
 	public $stack = array();
 
+	/**
+	 * Holds functions added to be called after popping an element off the stack.
+	 *
+	 * Listeners are passed the WP_HTML_Token for the item that was removed.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @var array
+	 */
+	private $after_pop_listeners = array();
+
 	/**
 	 * Whether a P element is in button scope currently.
 	 *
@@ -428,5 +439,39 @@ public function after_element_pop( $item ) {
 				$this->has_p_in_button_scope = $this->has_element_in_button_scope( 'P' );
 				break;
 		}
+
+		// Call any listeners that are registered.
+		foreach ( $this->after_pop_listeners as $listener ) {
+			call_user_func( $listener, $item );
+		}
+	}
+
+	/**
+	 * Creates a context in which a given listener is called after
+	 * popping an element off of the stack of open elements.
+	 *
+	 * It's unlikely that you will need this function. It exists
+	 * to aid an optimization in the `WP_HTML_Processor` and the
+	 * strange form of calling a generator inside a `foreach`
+	 * loop ensures that proper cleanup of the listener occurs.
+	 *
+	 * Example:
+	 *
+	 *     $did_close  = false;
+	 *     $closed_a_p = function ( $item ) use ( &$did_close ) { $did_close = 'P' === $item->node_name; };
+	 *     foreach ( $stack_of_open_elements->with_pop_listener( $closed_a_p ) ) {
+	 *         while ( ! $did_close && $processor->next_tag() ) {
+	 *             // This loop executes until _any_ P element is closed.
+	 *         }
+	 *     }
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param callable $listener Called with the WP_HTML_Token for the item that was popped off of the stack.
+	 */
+	public function with_pop_listener( $listener ) {
+		$this->after_pop_listeners[] = $listener;
+		yield;
+		array_pop( $this->after_pop_listeners );
 	}
 }
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 b8e1093054726..c85ce07fe1c81 100644
--- a/src/wp-includes/html-api/class-wp-html-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-processor.php
@@ -322,7 +322,7 @@ public function __construct( $html, $use_the_static_create_methods_instead = nul
 	 * be found or if content in the document caused the processor
 	 * to give up and abort processing.
 	 *
-	 * Example
+	 * Example:
 	 *
 	 *     $processor = WP_HTML_Processor::create_fragment( '<template><strong><button><em><p><em>' );
 	 *     false === $processor->next_tag();
@@ -473,6 +473,176 @@ public function matches_breadcrumbs( $breadcrumbs ) {
 		return false;
 	}
 
+	/**
+	 * Returns the raw HTML content inside a matched tag.
+	 *
+	 * "Markup" differs from inner HTML in that it returns the raw HTML inside the matched tag.
+	 * This means that it's possible this returns HTML without matching tags, or with HTML attributes
+	 * serialized differently than a DOM API would return.
+	 *
+	 * Example:
+	 *
+	 *     $processor = WP_HTML_Processor::createFragment( '<div><p>Inside <em>P</em> <i>tags</div>' );
+	 *     $processor->next_tag( 'P' );
+	 *     'Inside <em>P</em> <i>tags' === $processor->get_raw_inner_markup();
+	 *
+	 * @since 6.4.0
+	 *
+	 * @throws Exception When unable to allocate a bookmark for internal tracking of the open tag.
+	 *
+	 * @return string|null The inner markup if available, else NULL.
+	 */
+	public function get_raw_inner_markup() {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$this->set_bookmark( 'opener' );
+		$found_tag = $this->step_until_tag_is_closed();
+		$this->set_bookmark( 'closer' );
+
+		if ( $found_tag ) {
+			$inner_markup = $this->substr_bookmarks( 'after', 'opener', 'before', 'closer' );
+		} else {
+			// If there's no closing tag then the inner markup continues to the end of the document.
+			$inner_markup = $this->substr_bookmark( 'after', 'opener' );
+		}
+
+		$this->seek( 'opener' );
+		$this->release_bookmark( 'opener' );
+		$this->release_bookmark( 'closer' );
+
+		return $inner_markup;
+	}
+
+	/**
+	 * Returns the raw HTML content around a matched tag, including the tag itself.
+	 *
+	 * "Markup" differs from outer HTML in that it returns the raw HTML inside the matched tag.
+	 * This means that it's possible this returns HTML without matching tags, or with HTML attributes
+	 * serialized differently than a DOM API would return.
+	 *
+	 * Example:
+	 *
+	 *     $processor = WP_HTML_Processor::createFragment( '<div><p>Inside <em>P</em> <i>tags</div>' );
+	 *     $processor->next_tag( 'P' );
+	 *     '<p>Inside <em>P</em> <i>tags' === $processor->get_raw_inner_markup();
+	 *
+	 * @since 6.4.0
+	 *
+	 * @throws Exception When unable to allocate a bookmark for internal tracking of the open tag.
+	 *
+	 * @return string|null The outer markup if available, else NULL.
+	 */
+	public function get_raw_outer_markup() {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$this->set_bookmark( 'opener' );
+		$start_tag = $this->current_token->node_name;
+		$found_tag = $this->step_until_tag_is_closed();
+		$this->set_bookmark( 'closer' );
+
+		if ( $found_tag ) {
+			$did_close    = $this->get_tag() === $start_tag && $this->is_tag_closer();
+			$end_position = $did_close ? 'after' : 'before';
+			$outer_markup = $this->substr_bookmarks( 'before', 'opener', $end_position, 'closer' );
+		} else {
+			// If there's no closing tag then the outer markup continues to the end of the document.
+			$outer_markup = $this->substr_bookmark( 'before', 'opener' );
+		}
+
+		$this->seek( 'opener' );
+		$this->release_bookmark( 'opener' );
+		$this->release_bookmark( 'closer' );
+
+		return $outer_markup;
+	}
+
+	/**
+	 * Replaces the raw HTML of the currently-matched tag's inner markup with new HTML.
+	 * This replaces the content between the tag opener and tag closer.
+	 *
+	 * @throws Exception When unable to set bookmark for internal tracking.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $new_html
+	 * @return bool|null Whether the contents were updated.
+	 */
+	public function set_raw_inner_markup( $new_html ) {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$this->set_bookmark( 'opener' );
+		$start_tag = $this->current_token->node_name;
+
+		if ( self::is_void( $start_tag ) ) {
+			$this->release_bookmark( 'opener' );
+			return true;
+		}
+
+		$found_tag = $this->step_until_tag_is_closed();
+		$this->set_bookmark( 'closer' );
+
+		if ( $found_tag ) {
+			$this->replace_using_bookmarks( $new_html, 'after', 'opener', 'before', 'closer' );
+		} else {
+			// If there's no closing tag then the inner markup continues to the end of the document.
+			$this->replace_using_bookmark( $new_html, 'after', 'opener' );
+		}
+
+		$this->seek( 'opener' );
+		$this->release_bookmark( 'opener' );
+		$this->release_bookmark( 'closer' );
+		return true;
+	}
+
+	/**
+	 * Replaces the raw HTML of the currently-matched tag with new HTML.
+	 * This replaces the entire contents of the tag including the tag itself.
+	 *
+	 * @throws Exception When unable to set bookmark for internal tracking.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $new_html
+	 * @return bool|null Whether the contents were updated.
+	 */
+	public function set_raw_outer_markup( $new_html ) {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$this->set_bookmark( 'opener' );
+		$start_tag = $this->current_token->node_name;
+
+		if ( self::is_void( $start_tag ) ) {
+			$this->replace_using_bookmarks( $new_html, 'before', 'opener', 'after', 'opener' );
+			$this->release_bookmark( 'opener' );
+			return true;
+		}
+
+		$found_tag = $this->step_until_tag_is_closed();
+		$this->set_bookmark( 'closer' );
+
+		if ( $found_tag ) {
+			$did_close    = $this->get_tag() === $start_tag && $this->is_tag_closer();
+			$end_position = $did_close ? 'after' : 'before';
+			$this->replace_using_bookmarks( $new_html, 'before', 'opener', $end_position, 'closer' );
+		} else {
+			// If there's no closing tag then the outer markup continues to the end of the document.
+			$this->replace_using_bookmark( $new_html, 'before', 'opener' );
+		}
+
+		$this->seek( 'opener' );
+		$this->release_bookmark( 'opener' );
+		$this->release_bookmark( 'closer' );
+		return true;
+	}
+
 	/**
 	 * Steps through the HTML document and stop at the next tag, if any.
 	 *
@@ -512,12 +682,9 @@ public function step( $node_to_process = self::PROCESS_NEXT_NODE ) {
 				$this->state->stack_of_open_elements->pop();
 			}
 
-			parent::next_tag( self::VISIT_EVERYTHING );
-		}
-
-		// Finish stepping when there are no more tokens in the document.
-		if ( null === $this->get_tag() ) {
-			return false;
+			if ( ! parent::next_tag( self::VISIT_EVERYTHING ) ) {
+				return false;
+			}
 		}
 
 		$this->state->current_token = new WP_HTML_Token(
@@ -555,7 +722,7 @@ public function step( $node_to_process = self::PROCESS_NEXT_NODE ) {
 	 *       to avoid creating the array copy on tag iteration. If this is done, it would likely
 	 *       be more useful to walk up the stack when yielding instead of starting at the top.
 	 *
-	 * Example
+	 * Example:
 	 *
 	 *     $processor = WP_HTML_Processor::create_fragment( '<p><strong><em><img></em></strong></p>' );
 	 *     $processor->next_tag( 'IMG' );
@@ -800,6 +967,136 @@ private function bookmark_tag() {
 		return "{$this->bookmark_counter}";
 	}
 
+	/**
+	 * Steps through the HTML document until the current open tag is closed.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @throws Exception When unable to allocate bookmark for internal tracking.
+	 *
+	 * @return bool|null true if a closing tag was found, false if not, and null if not starting at a matched tag.
+	 */
+	private function step_until_tag_is_closed() {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		/** @var WP_HTML_Token $start Reference to the opening tag when calling this function. */
+		$start = $this->current_token;
+
+		/** @var bool $keep_searching Whether to continue scanning for a point where the opening tag is closed. */
+		$keep_searching = true;
+
+		/**
+		 * Sets a flag indicating that the starting tag has been closed once
+		 * it's popped from the stack of open elements. This is a listener function.
+		 *
+		 * @since 6.4.0
+		 *
+		 * @see WP_HTML_Open_Elements::with_pop_listener()
+		 *
+		 * @param WP_HTML_Token $node Node that was popped.
+		 */
+		$tag_is_closed = function ( $node ) use ( &$keep_searching, $start ) {
+			if ( $node === $start ) {
+				$keep_searching = false;
+			}
+		};
+
+		/*
+		 * Normally, when stepping into each new elements, it would be required to walk up the
+		 * stack of open elements and look to see if the starting tag is still open, if it's
+		 * on the stack. By listening for elements that are popped from the stack, however, it's
+		 * possible to know if the starting tag has been closed without anything more than a
+		 * constant boolean access, as the listener is called for each tag that's closed.
+		 *
+		 * The use of the `foreach` here creates a context which ensures that the listener is
+		 * properly removed and cleaned up without having to manually remove it.
+		 */
+		foreach ( $this->state->stack_of_open_elements->with_pop_listener( $tag_is_closed ) as $_ ) {
+			// Find where the tag is closed by stepping forward until it's no longer on the stack of open elements.
+			do {
+				$found_tag = $this->step();
+			} while ( $found_tag && $keep_searching );
+		}
+
+		return $found_tag;
+	}
+
+	/**
+	 * Replaces content in the HTML document from a bookmark to the end of the document.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html                New HTML to insert into document.
+	 * @param string $start_position      "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start_bookmark_name Bookmark name at which to start clipping.
+	 */
+	private function replace_using_bookmark( $html, $start_position, $start_bookmark_name ) {
+		$start_bookmark = $this->bookmarks[ "_{$start_bookmark_name}" ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start_offset, strlen( $this->html ), $html );
+		$this->apply_attributes_updates();
+	}
+
+	/**
+	 * Replaces content in the HTML document from one bookmark to another.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html                New HTML to insert into document.
+	 * @param string $start_position      "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start_bookmark_name Bookmark name at which to start clipping.
+	 * @param string $end_position        "before" to clip before bookmark, "after" to clip after.
+	 * @param string $end_bookmark_name   Bookmark name at which to end clipping.
+	 */
+	private function replace_using_bookmarks( $html, $start_position, $start_bookmark_name, $end_position, $end_bookmark_name ) {
+		$start_bookmark = $this->bookmarks[ "_{$start_bookmark_name}" ];
+		$end_bookmark   = $this->bookmarks[ "_{$end_bookmark_name}" ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+		$end_offset     = 'before' === $end_position ? $end_bookmark->start : $end_bookmark->end + 1;
+
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start_offset, $end_offset, $html );
+		$this->apply_attributes_updates();
+	}
+
+	/**
+	 * Returns a substring of the input HTML document from a bookmark until the end.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $start_position      "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start_bookmark_name Bookmark name at which to start clipping.
+	 * @return string Clipped substring of input HTMl document.
+	 */
+	private function substr_bookmark( $start_position, $start_bookmark_name ) {
+		$start_bookmark = $this->bookmarks[ "_{$start_bookmark_name}" ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+
+		return substr( $this->html, $start_offset );
+	}
+
+	/**
+	 * Returns a substring of the input HTML document delimited by bookmarks.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $start_position      "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start_bookmark_name Bookmark name at which to start clipping.
+	 * @param string $end_position        "before" to clip before bookmark, "after" to clip after.
+	 * @param string $end_bookmark_name   Bookmark name at which to end clipping.
+	 * @return string Clipped substring of input HTMl document.
+	 */
+	private function substr_bookmarks( $start_position, $start_bookmark_name, $end_position, $end_bookmark_name ) {
+		$start_bookmark = $this->bookmarks[ "_{$start_bookmark_name}" ];
+		$end_bookmark   = $this->bookmarks[ "_{$end_bookmark_name}" ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+		$end_offset     = 'before' === $end_position ? $end_bookmark->start : $end_bookmark->end + 1;
+
+		return substr( $this->html, $start_offset, $end_offset - $start_offset );
+	}
+
 	/*
 	 * HTML semantic overrides for Tag Processor
 	 */
diff --git a/src/wp-includes/html-api/class-wp-html-tag-processor.php b/src/wp-includes/html-api/class-wp-html-tag-processor.php
index 19cca778ea6ee..3ad836137a6fb 100644
--- a/src/wp-includes/html-api/class-wp-html-tag-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-tag-processor.php
@@ -1584,7 +1584,7 @@ private function class_name_updates_to_attributes_updates() {
 	 * @param int $shift_this_point Accumulate and return shift for this position.
 	 * @return int How many bytes the given pointer moved in response to the updates.
 	 */
-	private function apply_attributes_updates( $shift_this_point = 0 ) {
+	protected function apply_attributes_updates( $shift_this_point = 0 ) {
 		if ( ! count( $this->lexical_updates ) ) {
 			return 0;
 		}
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php
new file mode 100644
index 0000000000000..922f3c18c84fe
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php
@@ -0,0 +1,126 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::get_raw_inner_markup()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorGetInnerMarkup extends WP_UnitTestCase {
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_inner_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_returns_null_when_not_on_a_matching_tag() {
+		$p = WP_HTML_Processor::createFragment( '<p><div><span></span></div>' );
+
+		$this->assertNull( $p->get_raw_inner_markup() );
+
+		$this->assertFalse( $p->next_tag( 'BUTTON' ), "Should not have found a BUTTON tag but stopped at {$p->get_tag()}." );
+		$this->assertNull( $p->get_raw_inner_markup() );
+	}
+
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_inner_markup
+	 *
+	 * @dataProvider data_html_with_inner_markup
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $expected_inner_markup Inner markup of target node.
+	 */
+	public function test_returns_appropriate_inner_markup( $html_with_target_node, $expected_inner_markup ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame( $expected_inner_markup, $p->get_raw_inner_markup(), 'Failed to return appropriate inner markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_inner_markup() {
+		$data = array(
+			'Void elements'                => array( '<img target>', '' ),
+			'Empty elements'               => array( '<div target></div>', '' ),
+			'Element containing only text' => array( '<div target>inside</div>', 'inside' ),
+			'Element with nested tags'     => array( '<div target>inside <span>the</span> div</div>', 'inside <span>the</span> div' ),
+			'Unclosed element'             => array( '<div target>This is <em>all</em> inside the DIV', 'This is <em>all</em> inside the DIV' ),
+			'Unclosed elements'            => array( '<div><div target>Inside <em>P</em> <i>tags</div>', 'Inside <em>P</em> <i>tags' ),
+			'Partially-closed element'     => array( '<div target>This is <em>all</em> inside the DIV</div', 'This is <em>all</em> inside the DIV</div' ),
+			'Implicitly-closed element'    => array( '<div><p target>Inside the P</div>Outside the P</p>', 'Inside the P' ),
+		);
+
+		$inner_html = <<<HTML
+			<p>This is inside the <strong>Match</strong></p>
+			<p><img></p>
+			<div>
+				<figure>
+					<img>
+					<figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+				</figure>
+			</div>
+HTML;
+
+		$html = <<<HTML
+			<div>
+				 <p>This is not in the match.
+				 <p>This is another paragraph not <a href="#">in</a> the match.
+			</div>
+			<div target>{$inner_html}</div>
+			<div>
+				 <p>This is also note in the match.</p>
+			</div>
+HTML;
+
+		$data['Complicated inner nesting'] = array( $html, $inner_html );
+
+		return $data;
+	}
+
+	/**
+	 * Ensures that the cursor isn't moved when getting the inner markup.
+	 * It should remain at the tag opener from where it was called.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_inner_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_preserves_cursor() {
+		$p = WP_HTML_Processor::createFragment( '<div><p><span target>The <code inner-target>cursor</code> should not move <em>unexpectedly</em>.</span></p></div>' );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame(
+			'The <code inner-target>cursor</code> should not move <em>unexpectedly</em>.',
+			$p->get_raw_inner_markup(),
+			'Failed to return appropriate inner markup.'
+		);
+
+		$this->assertSame( 'SPAN', $p->get_tag(), "Should have remained on SPAN, but found {$p->get_tag()} instead." );
+		$this->assertFalse( $p->is_tag_closer(), 'Should have remained on SPAN opening tag, but stopped at closing tag instead.' );
+
+		$p->next_tag();
+		$this->assertNotNull( $p->get_attribute( 'inner-target' ), "Expected to move to inner CODE element, but found {$p->get_tag()} instead." );
+	}
+}
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php
new file mode 100644
index 0000000000000..156966018c990
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php
@@ -0,0 +1,128 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::get_raw_outer_markup()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorGetOuterMarkup extends WP_UnitTestCase {
+	/**
+	 * Ensures that it's not possible to get inner contents when not stopped at a tag in the HTML.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_outer_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_returns_null_when_not_on_a_matching_tag() {
+		$p = WP_HTML_Processor::createFragment( '<p><div><span></span></div>' );
+
+		$this->assertNull( $p->get_raw_outer_markup() );
+
+		$this->assertFalse( $p->next_tag( 'BUTTON' ), "Should not have found a BUTTON tag but stopped at {$p->get_tag()}." );
+		$this->assertNull( $p->get_raw_outer_markup() );
+	}
+
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_outer_markup
+	 *
+	 * @dataProvider data_html_with_outer_markup
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $expected_outer_markup Outer markup of target node.
+	 */
+	public function test_returns_appropriate_outer_markup( $html_with_target_node, $expected_outer_markup ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame( $expected_outer_markup, $p->get_raw_outer_markup(), 'Failed to return appropriate outer markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_outer_markup() {
+		$data = array(
+			'Void elements'                => array( '<img target>', '<img target>' ),
+			'Empty elements'               => array( '<div target></div>', '<div target></div>' ),
+			'Element containing only text' => array( '<div target>inside</div>', '<div target>inside</div>' ),
+			'Element with nested tags'     => array( '<div target>inside <span>the</span> div</div>', '<div target>inside <span>the</span> div</div>' ),
+			'Unclosed element'             => array( '<div target>This is <em>all</em> inside the DIV', '<div target>This is <em>all</em> inside the DIV' ),
+			'Unclosed elements'            => array( '<div><p target>Inside <em>P</em> <i>tags</div>', '<p target>Inside <em>P</em> <i>tags' ),
+			'Partially-closed element'     => array( '<div target>This is <em>all</em> inside the DIV</div', '<div target>This is <em>all</em> inside the DIV</div' ),
+			'Implicitly-closed element'    => array( '<div><p target>Inside the P</div>Outside the P</p>', '<p target>Inside the P' ),
+		);
+
+		$inner_html = <<<HTML
+			<p>This is inside the <strong>Match</strong></p>
+			<p><img></p>
+			<div>
+				<figure>
+					<img>
+					<figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+				</figure>
+			</div>
+HTML;
+
+		$html = <<<HTML
+			<div>
+				<p>This is not in the match.
+				<p>This is another paragraph not <a href="#">in</a> the match.
+			</div>
+			<div target>{$inner_html}</div>
+			<div>
+				<p>This is also note in the match.</p>
+			</div>
+HTML;
+
+		$data['Complicated inner nesting'] = array( $html, "<div target>{$inner_html}</div>" );
+
+		return $data;
+	}
+
+	/**
+	 * Ensures that the cursor isn't moved when getting the outer markup.
+	 * It should remain at the tag opener from where it was called.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_raw_outer_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_preserves_cursor() {
+		$p = WP_HTML_Processor::createFragment( '<div><p><span target>The <code inner-target>cursor</code> should not move <em>unexpectedly</em>.</span></p></div>' );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame(
+			'<span target>The <code inner-target>cursor</code> should not move <em>unexpectedly</em>.</span>',
+			$p->get_raw_outer_markup(),
+			'Failed to return appropriate outer markup.'
+		);
+
+		$this->assertSame( 'SPAN', $p->get_tag(), "Should have remained on SPAN, but found {$p->get_tag()} instead." );
+		$this->assertFalse( $p->is_tag_closer(), 'Should have remained on SPAN opening tag, but stopped at closing tag instead.' );
+
+		$p->next_tag();
+		$this->assertNotNull( $p->get_attribute( 'inner-target' ), "Expected to move to inner CODE element, but found {$p->get_tag()} instead." );
+	}
+}
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorSetInnerMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorSetInnerMarkup.php
new file mode 100644
index 0000000000000..02d1546e27494
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorSetInnerMarkup.php
@@ -0,0 +1,131 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::set_raw_inner_markup()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorSetInnerMarkup extends WP_UnitTestCase {
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::set_raw_inner_markup
+	 *
+	 * @dataProvider data_html_with_inner_markup_changes
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $new_markup            HTML for replacing the inner markup of the target node.
+	 * @param string $expected_output       New HTMl after replacing inner markup.
+	 */
+	public function test_replaces_inner_html_appropriately( $html_with_target_node, $new_markup, $expected_output ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertTrue( $p->set_raw_inner_markup( $new_markup ), 'Failed to set inner markup.' );
+		$this->assertSame( $expected_output, $p->get_updated_html(), 'Failed to appropriately set inner markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_inner_markup_changes() {
+		$data = array(
+			'Void element'                        => array( '<img target>', '', '<img target>' ),
+			'Void element inside text'            => array( 'before<img src="atat.png" loading=lazy target>after', '', 'before<img src="atat.png" loading=lazy target>after' ),
+			'Void element inside another element' => array( '<p>Look at this <img target> graph.</p>', '', '<p>Look at this <img target> graph.</p>' ),
+			'Empty elements'                      => array( '<div target></div>', '', '<div target></div>' ),
+			'Element with nested tags'            => array( '<div target>inside <span>the</span> div</div>', '', '<div target></div>' ),
+			'Element inside another element'      => array( '<div>inside <span target>the</span> div</div>', '', '<div>inside <span target></span> div</div>' ),
+			'Unclosed element'                    => array( '<div target>This is <em>all</em> inside the DIV', '', '<div target>' ),
+			'Unclosed nested element'             => array( '<div><p target>One thought<p>And another', '', '<div><p target><p>And another' ),
+			'Partially-closed element'            => array( '<div target>This is <em>all</em> inside the DIV</div', '', '<div target>' ),
+			'Implicitly-closed element'           => array( '<div><p target>Inside the P</div>Outside the P</p>', '', '<div><p target></div>Outside the P</p>' ),
+
+			'Text markup'                         => array( '<span target></span>', 'Today is the best day to start.', '<span target>Today is the best day to start.</span>' ),
+			'Text with ampersand (raw)'           => array( '<span target></span>', 'Today & yesterday are the best days to start.', '<span target>Today & yesterday are the best days to start.</span>' ),
+			'Text with tag (raw)'                 => array( '<span target></span>', 'Yesterday <em>was</em> the best day to start.', '<span target>Yesterday <em>was</em> the best day to start.</span>' ),
+			'Text with unclosed tag (raw)'        => array( '<span target></span>', 'Yesterday <em>was the best day to start.', '<span target>Yesterday <em>was the best day to start.</span>' ),
+			'Text with ending tag (raw)'          => array( '<span target></span>', 'Here is no </div>', '<span target>Here is no </div></span>' ),
+			'Text with scope-creating tag (raw)'  => array( '<span target></span>', '<p>Start<p>Finish<p>Repeat', '<span target><p>Start<p>Finish<p>Repeat</span>' ),
+			'Text with scope-ending tag (raw)'    => array( '<span target></span>', 'Sneaky closing </span> No more span.', '<span target>Sneaky closing </span> No more span.</span>' ),
+		);
+
+		$inner_html = <<<HTML
+			<p>This is inside the <strong>Match</strong></p>
+			<p><img></p>
+			<div>
+				  <figure>
+					   <img>
+					   <figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+				  </figure>
+			</div>
+HTML;
+
+		$prefix = <<<HTML
+			<div>
+				<p>This is not in the match.
+				<p>This is another paragraph not <a href="#">in</a> the match.
+			</div>
+			<div target>
+HTML;
+
+		/*
+		 * Removing the indent on this first line keeps the test easy to reason about,
+		 * otherwise extra indents appear after removing the inner content, because
+		 * that indentation before and after is whitespace and not part of the tag.
+		 */
+		$suffix = <<<HTML
+</div>
+			<div>
+				<p>This is also note in the match.</p>
+			</div>
+HTML;
+
+		$data['Complicated inner nesting'] = array( $prefix . $inner_html . $suffix, '', $prefix . $suffix );
+
+		return $data;
+	}
+
+	/**
+	 * Ensures that the cursor isn't moved when setting the inner markup. It should
+	 * remain at the same location as the tag opener where it was called.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::set_raw_inner_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_preserves_cursor() {
+		$p = WP_HTML_Processor::createFragment( '<div><p><span>The <code target>cursor</code> should not move <em next-target>unexpectedly</em>.</span></p></div>' );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertTrue( $p->set_raw_inner_markup( '<img next-target>' ) );
+		$this->assertSame(
+			'<div><p><span>The <code target><img next-target></code> should not move <em next-target>unexpectedly</em>.</span></p></div>',
+			$p->get_updated_html(),
+			'Failed to replace appropriate inner markup.'
+		);
+
+		$this->assertSame( 'CODE', $p->get_tag(), "Should have remained on CODE, but found {$p->get_tag()} instead." );
+
+		$p->next_tag();
+		$this->assertNotNull( $p->get_attribute( 'next-target' ), "Expected to move to inserted IMG element, but found {$p->get_tag()} instead." );
+	}
+}
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorSetOuterMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorSetOuterMarkup.php
new file mode 100644
index 0000000000000..b5e729703920a
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorSetOuterMarkup.php
@@ -0,0 +1,131 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::set_raw_outer_markup()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorSetOuterMarkup extends WP_UnitTestCase {
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::set_raw_outer_markup
+	 *
+	 * @dataProvider data_html_with_outer_markup_changes
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $new_markup            HTML for replacing the outer markup of the target node.
+	 * @param string $expected_output       New HTMl after replacing outer markup.
+	 */
+	public function test_replaces_outer_html_appropriately( $html_with_target_node, $new_markup, $expected_output ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertTrue( $p->set_raw_outer_markup( $new_markup ), 'Failed to set outer markup.' );
+		$this->assertSame( $expected_output, $p->get_updated_html(), 'Failed to appropriately set outer markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_outer_markup_changes() {
+		$data = array(
+			'Void element'                        => array( '<img target>', '', '' ),
+			'Void element inside text'            => array( 'before<img src="atat.png" loading=lazy target>after', '', 'beforeafter' ),
+			'Void element inside another element' => array( '<p>Look at this <img target> graph.</p>', '', '<p>Look at this  graph.</p>' ),
+			'Empty elements'                      => array( '<div target></div>', '', '' ),
+			'Element with nested tags'            => array( '<div target>inside <span>the</span> div</div>', '', '' ),
+			'Element inside another element'      => array( '<div>inside <span target>the</span> div</div>', '', '<div>inside  div</div>' ),
+			'Unclosed element'                    => array( '<div target>This is <em>all</em> inside the DIV', '', '' ),
+			'Unclosed nested element'             => array( '<div><p target>One thought<p>And another', '', '<div><p>And another' ),
+			'Partially-closed element'            => array( '<div target>This is <em>all</em> inside the DIV</div', '', '' ),
+			'Implicitly-closed element'           => array( '<div><p target>Inside the P</div>Outside the P</p>', '', '<div></div>Outside the P</p>' ),
+
+			'Text markup'                         => array( '<span target></span>', 'Today is the best day to start.', 'Today is the best day to start.' ),
+			'Text with ampersand (raw)'           => array( '<span target></span>', 'Today & yesterday are the best days to start.', 'Today & yesterday are the best days to start.' ),
+			'Text with tag (raw)'                 => array( '<span target></span>', 'Yesterday <em>was</em> the best day to start.', 'Yesterday <em>was</em> the best day to start.' ),
+			'Text with unclosed tag (raw)'        => array( '<span target></span>', 'Yesterday <em>was the best day to start.', 'Yesterday <em>was the best day to start.' ),
+			'Text with ending tag (raw)'          => array( '<span target></span>', 'Here is no </div>', 'Here is no </div>' ),
+			'Text with scope-creating tag (raw)'  => array( '<span target></span>', '<p>Start<p>Finish<p>Repeat', '<p>Start<p>Finish<p>Repeat' ),
+			'Text with scope-ending tag (raw)'    => array( '<span target></span>', 'Sneaky closing </span> No more span.', 'Sneaky closing </span> No more span.' ),
+		);
+
+		/*
+		 * Removing the indent on this variable keeps the test easy to reason about,
+		 * otherwise extra indents appear after removing the inner content, because
+		 * that indentation before and after is whitespace and not part of the tag.
+		 */
+		$inner_html = <<<HTML
+<div target>
+	<p>This is inside the <strong>Match</strong></p>
+	<p><img></p>
+	<div>
+		  <figure>
+			   <img>
+			   <figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+		  </figure>
+	</div>
+</div>
+HTML;
+
+		$prefix = <<<HTML
+			<div>
+				<p>This is not in the match.
+				<p>This is another paragraph not <a href="#">in</a> the match.
+			</div>
+HTML;
+
+		$suffix = <<<HTML
+			<div>
+				<p>This is also note in the match.</p>
+			</div>
+HTML;
+
+		$data['Complicated inner nesting'] = array( $prefix . $inner_html . $suffix, '', $prefix . $suffix );
+
+		return $data;
+	}
+
+	/**
+	 * Ensures that the cursor isn't moved when setting the outer markup. It should
+	 * remain at the same location as the tag opener where it was called.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::set_raw_outer_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_preserves_cursor() {
+		$p = WP_HTML_Processor::createFragment( '<div><p><span>The <code target>cursor</code> should not move <em next-target>unexpectedly</em>.</span></p></div>' );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertTrue( $p->set_raw_outer_markup( '<img>' ) );
+		$this->assertSame(
+			'<div><p><span>The <img> should not move <em next-target>unexpectedly</em>.</span></p></div>',
+			$p->get_updated_html(),
+			'Failed to replace appropriate outer markup.'
+		);
+
+		$this->assertSame( 'IMG', $p->get_tag(), "Should have remained on IMG, but found {$p->get_tag()} instead." );
+
+		$p->next_tag();
+		$this->assertNotNull( $p->get_attribute( 'next-target' ), "Expected to move to following EM element, but found {$p->get_tag()} instead." );
+	}
+}