diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index be37097220129..c1eb2c878a115 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -3306,89 +3306,49 @@ static function( $matches ) {
  *
  * @since 5.1.0
  * @since 5.6.0 Removed 'noreferrer' relationship.
+ * @since 6.3.0 Rely on the Tag Processor for HTML searching and modification.
  *
  * @param string $text Content that may contain HTML A elements.
  * @return string Converted content.
  */
 function wp_targeted_link_rel( $text ) {
-	// Don't run (more expensive) regex if no links with targets.
+	// Don't run (more expensive) code if no links with targets are possible.
 	if ( stripos( $text, 'target' ) === false || stripos( $text, '<a ' ) === false || is_serialized( $text ) ) {
 		return $text;
 	}
 
-	$script_and_style_regex = '/<(script|style).*?<\/\\1>/si';
-
-	preg_match_all( $script_and_style_regex, $text, $matches );
-	$extra_parts = $matches[0];
-	$html_parts  = preg_split( $script_and_style_regex, $text );
-
-	foreach ( $html_parts as &$part ) {
-		$part = preg_replace_callback( '|<a\s([^>]*target\s*=[^>]*)>|i', 'wp_targeted_link_rel_callback', $part );
-	}
-
-	$text = '';
-	for ( $i = 0; $i < count( $html_parts ); $i++ ) {
-		$text .= $html_parts[ $i ];
-		if ( isset( $extra_parts[ $i ] ) ) {
-			$text .= $extra_parts[ $i ];
+	$p = new WP_HTML_Tag_Processor( $text );
+	while ( $p->next_tag( 'a' ) ) {
+		if ( ! is_string( $p->get_attribute( 'target' ) ) ) {
+			continue;
 		}
-	}
 
-	return $text;
-}
+		$href      = $p->get_attribute( 'href' );
+		$rel       = $p->get_attribute( 'rel' );
+		$rel       = is_string( $rel ) ? $rel : '';
+		$link_text = sprintf( 'href="%s" rel="%s"', esc_attr( $href ), esc_attr( $rel ) );
 
-/**
- * Callback to add `rel="noopener"` string to HTML A element.
- *
- * Will not duplicate an existing 'noopener' value to avoid invalidating the HTML.
- *
- * @since 5.1.0
- * @since 5.6.0 Removed 'noreferrer' relationship.
- *
- * @param array $matches Single match.
- * @return string HTML A Element with `rel="noopener"` in addition to any existing values.
- */
-function wp_targeted_link_rel_callback( $matches ) {
-	$link_html          = $matches[1];
-	$original_link_html = $link_html;
-
-	// Consider the HTML escaped if there are no unescaped quotes.
-	$is_escaped = ! preg_match( '/(^|[^\\\\])[\'"]/', $link_html );
-	if ( $is_escaped ) {
-		// Replace only the quotes so that they are parsable by wp_kses_hair(), leave the rest as is.
-		$link_html = preg_replace( '/\\\\([\'"])/', '$1', $link_html );
-	}
-
-	$atts = wp_kses_hair( $link_html, wp_allowed_protocols() );
-
-	/**
-	 * Filters the rel values that are added to links with `target` attribute.
-	 *
-	 * @since 5.1.0
-	 *
-	 * @param string $rel       The rel values.
-	 * @param string $link_html The matched content of the link tag including all HTML attributes.
-	 */
-	$rel = apply_filters( 'wp_targeted_link_rel', 'noopener', $link_html );
-
-	// Return early if no rel values to be added or if no actual target attribute.
-	if ( ! $rel || ! isset( $atts['target'] ) ) {
-		return "<a $original_link_html>";
-	}
-
-	if ( isset( $atts['rel'] ) ) {
-		$all_parts = preg_split( '/\s/', "{$atts['rel']['value']} $rel", -1, PREG_SPLIT_NO_EMPTY );
-		$rel       = implode( ' ', array_unique( $all_parts ) );
-	}
-
-	$atts['rel']['whole'] = 'rel="' . esc_attr( $rel ) . '"';
-	$link_html            = implode( ' ', array_column( $atts, 'whole' ) );
+		/**
+		 * Filters the rel values that are added to links with `target` attribute.
+		 *
+		 * @TODO: Some plugins scan the link text, though they mostly scan for URL patterns.
+		 *        We need to provide the existing tag HTML or find a way to update filters.
+		 *
+		 * @since 5.1.0
+		 *
+		 * @param string $rel       The rel values.
+		 * @param string $link_html The matched content of the link tag including all HTML attributes.
+		 */
+		$updated_rel = apply_filters( 'wp_targeted_link_rel', 'noopener', $link_text );
+		if ( ! $updated_rel ) {
+			continue;
+		}
 
-	if ( $is_escaped ) {
-		$link_html = preg_replace( '/[\'"]/', '\\\\$0', $link_html );
+		$all_rel_parts = preg_split( '/\s/', "$rel $updated_rel", -1, PREG_SPLIT_NO_EMPTY );
+		$p->set_attribute( 'rel', implode( ' ', array_unique( $all_rel_parts ) ) );
 	}
 
-	return "<a $link_html>";
+	return $p->get_updated_html();
 }
 
 /**
diff --git a/tests/phpunit/tests/formatting/wpTargetedLinkRel.php b/tests/phpunit/tests/formatting/wpTargetedLinkRel.php
index 75a247e212caa..1fc74a25cc560 100644
--- a/tests/phpunit/tests/formatting/wpTargetedLinkRel.php
+++ b/tests/phpunit/tests/formatting/wpTargetedLinkRel.php
@@ -11,25 +11,25 @@ class Tests_Formatting_wpTargetedLinkRel extends WP_UnitTestCase {
 	public function test_add_to_links_with_target_blank() {
 		$content  = '<p>Links: <a href="/" target="_blank">No rel</a></p>';
 		$expected = '<p>Links: <a href="/" target="_blank" rel="noopener">No rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_add_to_links_with_target_foo() {
 		$content  = '<p>Links: <a href="/" target="foo">No rel</a></p>';
 		$expected = '<p>Links: <a href="/" target="foo" rel="noopener">No rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_target_as_first_attribute() {
 		$content  = '<p>Links: <a target="_blank" href="#">No rel</a></p>';
 		$expected = '<p>Links: <a target="_blank" href="#" rel="noopener">No rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_add_to_existing_rel() {
 		$content  = '<p>Links: <a href="/" rel="existing values" target="_blank">Existing rel</a></p>';
 		$expected = '<p>Links: <a href="/" rel="existing values noopener" target="_blank">Existing rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_no_duplicate_values_added() {
@@ -41,31 +41,31 @@ public function test_no_duplicate_values_added() {
 	public function test_rel_with_single_quote_delimiter() {
 		$content  = '<p>Links: <a href="/" rel=\'existing values\' target="_blank">Existing rel</a></p>';
 		$expected = '<p>Links: <a href="/" rel="existing values noopener" target="_blank">Existing rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_rel_with_no_delimiter() {
 		$content  = '<p>Links: <a href="/" rel=existing target="_blank">Existing rel</a></p>';
 		$expected = '<p>Links: <a href="/" rel="existing noopener" target="_blank">Existing rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_rel_value_spaced_and_no_delimiter() {
 		$content  = '<p>Links: <a href="/" rel = existing target="_blank">Existing rel</a></p>';
 		$expected = '<p>Links: <a href="/" rel="existing noopener" target="_blank">Existing rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_escaped_quotes() {
 		$content  = '<p>Links: <a href=\"/\" rel=\"existing values\" target=\"_blank\">Existing rel</a></p>';
 		$expected = '<p>Links: <a href=\"/\" rel=\"existing values noopener\" target=\"_blank\">Existing rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_ignore_links_with_no_target() {
 		$content  = '<p>Links: <a href="/" target="_blank">Change me</a> <a href="/">Do not change me</a></p>';
 		$expected = '<p>Links: <a href="/" target="_blank" rel="noopener">Change me</a> <a href="/">Do not change me</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	/**
@@ -77,7 +77,7 @@ public function test_ignore_if_wp_targeted_link_rel_nulled() {
 		add_filter( 'wp_targeted_link_rel', '__return_empty_string' );
 		$content  = '<p>Links: <a href="/" target="_blank">Do not change me</a></p>';
 		$expected = '<p>Links: <a href="/" target="_blank">Do not change me</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	/**
@@ -95,7 +95,7 @@ public function test_wp_targeted_link_rel_filters_run() {
 			)
 		);
 
-		$this->assertSame( $expected, $post->post_content );
+		$this->assertEqualMarkup( $expected, $post->post_content );
 	}
 
 	/**
@@ -106,7 +106,7 @@ public function test_wp_targeted_link_rel_filters_run() {
 	public function test_wp_targeted_link_rel_should_preserve_json() {
 		$content  = '<p>Links: <a href=\"\/\" target=\"_blank\">No rel<\/a><\/p>';
 		$expected = '<p>Links: <a href=\"\/\" target=\"_blank\" rel=\"noopener\">No rel<\/a><\/p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	/**
@@ -117,7 +117,7 @@ public function test_wp_targeted_link_rel_should_preserve_json() {
 	public function test_wp_targeted_link_rel_skips_style_and_scripts() {
 		$content  = '<style><a href="/" target=a></style><p>Links: <script>console.log("<a href=\'/\' target=a>hi</a>");</script><script>alert(1);</script>here <a href="/" target=_blank>aq</a></p><script>console.log("<a href=\'last\' target=\'_blank\'")</script>';
 		$expected = '<style><a href="/" target=a></style><p>Links: <script>console.log("<a href=\'/\' target=a>hi</a>");</script><script>alert(1);</script>here <a href="/" target="_blank" rel="noopener">aq</a></p><script>console.log("<a href=\'last\' target=\'_blank\'")</script>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	/**
@@ -128,13 +128,13 @@ public function test_wp_targeted_link_rel_skips_style_and_scripts() {
 	public function test_ignore_entirely_serialized_content() {
 		$content  = 'a:1:{s:4:"html";s:52:"<p>Links: <a href="/" target="_blank">No Rel</a></p>";}';
 		$expected = 'a:1:{s:4:"html";s:52:"<p>Links: <a href="/" target="_blank">No Rel</a></p>";}';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 	public function test_wp_targeted_link_rel_tab_separated_values_are_split() {
 		$content  = "<p>Links: <a href=\"/\" target=\"_blank\" rel=\"ugc\t\tnoopener\t\">No rel</a></p>";
 		$expected = '<p>Links: <a href="/" target="_blank" rel="ugc noopener">No rel</a></p>';
-		$this->assertSame( $expected, wp_targeted_link_rel( $content ) );
+		$this->assertEqualMarkup( $expected, wp_targeted_link_rel( $content ) );
 	}
 
 }
diff --git a/tests/phpunit/tests/rest-api/rest-attachments-controller.php b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
index 55cf74f3d72af..9b6ca6c21d0dc 100644
--- a/tests/phpunit/tests/rest-api/rest-attachments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
@@ -1211,11 +1211,11 @@ public function verify_attachment_roundtrip( $input = array(), $expected_output
 		}
 
 		// Compare expected API output to actual API output.
-		$this->assertSame( $expected_output['title']['raw'], $actual_output['title']['raw'] );
+		$this->assertEqualMarkup( $expected_output['title']['raw'], $actual_output['title']['raw'] );
 		$this->assertSame( $expected_output['title']['rendered'], trim( $actual_output['title']['rendered'] ) );
-		$this->assertSame( $expected_output['description']['raw'], $actual_output['description']['raw'] );
+		$this->assertEqualMarkup( $expected_output['description']['raw'], $actual_output['description']['raw'] );
 		$this->assertSame( $expected_output['description']['rendered'], trim( $actual_output['description']['rendered'] ) );
-		$this->assertSame( $expected_output['caption']['raw'], $actual_output['caption']['raw'] );
+		$this->assertEqualMarkup( $expected_output['caption']['raw'], $actual_output['caption']['raw'] );
 		$this->assertSame( $expected_output['caption']['rendered'], trim( $actual_output['caption']['rendered'] ) );
 
 		// Compare expected API output to WP internal values.
diff --git a/tests/phpunit/tests/widgets/wpWidgetMediaImage.php b/tests/phpunit/tests/widgets/wpWidgetMediaImage.php
index 3f96cf34ebb82..3b2ea72426738 100644
--- a/tests/phpunit/tests/widgets/wpWidgetMediaImage.php
+++ b/tests/phpunit/tests/widgets/wpWidgetMediaImage.php
@@ -449,12 +449,23 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
+		$p = new WP_HTML_Tag_Processor( $output );
+
 		// No default title.
-		$this->assertStringNotContainsString( 'title="', $output );
+		$this->assertTrue( $p->next_tag( 'a' ), 'Failed to find wrapping A tag.' );
+		$this->assertNull( $p->get_attribute( 'title' ), "Should not have returned title but found: {$p->get_attribute( 'title' )}." );
+
 		// Default image classes.
-		$this->assertStringContainsString( 'class="image wp-image-' . $attachment_id, $output );
-		$this->assertStringContainsString( 'style="max-width: 100%; height: auto;"', $output );
-		$this->assertStringContainsString( 'alt=""', $output );
+		$this->assertTrue( $p->next_tag( 'img' ), 'Failed to find IMG tag.' );
+		$expected_classes = array( 'image', "wp-image-{$attachment_id}" );
+		$this->assertSame(
+			$expected_classes,
+			array_intersect( $expected_classes, preg_split( '~[ \t\f\r\n]~', $p->get_attribute( 'class' ), -1, PREG_SPLIT_NO_EMPTY ) ),
+			"Expected 'image' and 'wp-image-{$attachment_id}' classes but instead found: {$p->get_attribute( 'class' )}"
+		);
+
+		$this->assertEquals( 'max-width: 100%; height: auto;', $p->get_attribute( 'style' ), "Found unexpected style values." );
+		$this->assertEquals( '', $p->get_attribute( 'alt' ), 'Expected to find empty alt attribute.' );
 
 		ob_start();
 		$widget->render_media(
@@ -470,13 +481,24 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
+		$p = new WP_HTML_Tag_Processor( $output );
+
 		// Custom image title.
-		$this->assertStringContainsString( 'title="Custom Title"', $output );
+		$this->assertTrue( $p->next_tag( 'a' ), 'Failed to find wrapping A tag.' );
+		$this->assertEquals( 'Custom Title', $p->get_attribute( 'title' ), 'Did not return proper title attribute.' );
+
 		// Custom image class.
-		$this->assertStringContainsString( 'class="image wp-image-' . $attachment_id . ' custom-class', $output );
-		$this->assertStringContainsString( 'alt="A flower"', $output );
-		$this->assertStringContainsString( 'width="100"', $output );
-		$this->assertStringContainsString( 'height="100"', $output );
+		$this->assertTrue( $p->next_tag( 'img' ), 'Failed to find IMG tag.' );
+		$expected_classes = array( 'image', "wp-image-{$attachment_id}", 'custom-class' );
+		$this->assertSame(
+			$expected_classes,
+			array_intersect( $expected_classes, preg_split( '~[ \t\f\r\n]~', $p->get_attribute( 'class' ), -1, PREG_SPLIT_NO_EMPTY ) ),
+			"Expected 'image', 'wp-image-{$attachment_id}', and 'custom-class' classes but instead found: {$p->get_attribute( 'class' )}"
+		);
+
+		$this->assertEquals( '100', $p->get_attribute( 'height' ), 'Returned wrong height attribute value.' );
+		$this->assertEquals( '100', $p->get_attribute( 'width' ), 'Returned wrong width attribute value.' );
+		$this->assertEquals( 'A flower', $p->get_attribute( 'alt' ), 'Returned wrong alt attribute value.' );
 
 		// Embeded images.
 		ob_start();
@@ -492,10 +514,13 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
+		$p = new WP_HTML_Tag_Processor( $output );
+
 		// Custom image class.
-		$this->assertStringContainsString( 'src="http://example.org/url/to/image.jpg"', $output );
-		$this->assertStringContainsString( 'decoding="async"', $output );
-		$this->assertStringContainsString( 'loading="lazy"', $output );
+		$this->assertTrue( $p->next_tag( 'img' ), 'Failed to find IMG tag.' );
+		$this->assertEquals( 'http://example.org/url/to/image.jpg', $p->get_attribute( 'src' ), 'Returned wrong src attribute value.' );
+		$this->assertEquals( 'async', $p->get_attribute( 'decoding' ), 'Returned wrong decoding attribute value.' );
+		$this->assertEquals( 'lazy', $p->get_attribute( 'loading' ), 'Returned wrong loading attribute value.' );
 
 		// Link settings.
 		ob_start();
@@ -507,12 +532,13 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
-		$link = '<a href="' . wp_get_attachment_url( $attachment_id ) . '"';
-		$this->assertStringContainsString( $link, $output );
-		$this->assertTrue( (bool) preg_match( '#<a href.*?>#', $output, $matches ) );
-		$this->assertStringNotContainsString( ' class="', $matches[0] );
-		$this->assertStringNotContainsString( ' rel="', $matches[0] );
-		$this->assertStringNotContainsString( ' target="', $matches[0] );
+		$p = new WP_HTML_Tag_Processor( $output );
+
+		$this->assertTrue( $p->next_tag( 'a' ), 'Failed to find A tag.' );
+		$this->assertEquals( wp_get_attachment_url( $attachment_id ), $p->get_attribute( 'href' ), 'Returned wrong href attribute value.' );
+		$this->assertNull( $p->get_attribute( 'class' ), "Should not have found class attribute but instead found: {$p->get_attribute( 'class' )}." );
+		$this->assertNull( $p->get_attribute( 'rel' ), "Should not have found rel attribute but instead found: {$p->get_attribute( 'rel' )}." );
+		$this->assertNull( $p->get_attribute( 'target' ), "Should not have found target attribute but instead found: {$p->get_attribute( 'target' )}." );
 
 		ob_start();
 		$widget->render_media(
@@ -526,10 +552,13 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
-		$this->assertStringContainsString( '<a href="' . get_attachment_link( $attachment_id ) . '"', $output );
-		$this->assertStringContainsString( 'class="custom-link-class"', $output );
-		$this->assertStringContainsString( 'rel="attachment"', $output );
-		$this->assertStringNotContainsString( 'target=""', $output );
+		$p = new WP_HTML_Tag_Processor( $output );
+
+		$this->assertTrue( $p->next_tag( 'a' ), 'Failed to find A tag.' );
+		$this->assertEquals( wp_get_attachment_link( $attachment_id ), $p->get_attribute( 'href' ), 'Returned wrong href attribute value.' );
+		$this->assertEquals( 'custom-link-class', $p->get_attribute( 'class' ), 'Returned wrong class attribute value.' );
+		$this->assertEquals( 'attachment', $p->get_attribute( 'rel' ), 'Returned wrong rel attribute value.' );
+		$this->assertNull( $p->get_attribute( 'target' ), "Should not have found target attribute but instead found: {$p->get_attribute( 'target' )}." );
 
 		ob_start();
 		$widget->render_media(
@@ -542,9 +571,12 @@ public function test_render_media() {
 		);
 		$output = ob_get_clean();
 
-		$this->assertStringContainsString( '<a href="https://example.org"', $output );
-		$this->assertStringContainsString( 'target="_blank"', $output );
-		$this->assertStringContainsString( 'rel="noopener"', $output );
+		$p = new WP_HTML_Tag_Processor( $output );
+
+		$this->assertTrue( $p->next_tag( 'a' ), 'Failed to find A tag.' );
+		$this->assertEquals( 'https://example.org', $p->get_attribute( 'href' ), 'Returned wrong href attribute value.' );
+		$this->assertEquals( 'noopener', $p->get_attribute( 'rel' ), 'Returned wrong rel attribute value.' );
+		$this->assertEquals( '_blank', $p->get_attribute( 'target' ), 'Returned wrong target attribute value.' );
 
 		// Populate caption in attachment.
 		wp_update_post(
@@ -562,6 +594,7 @@ public function test_render_media() {
 			)
 		);
 		$output = ob_get_clean();
+		// @TODO: Update this test once $p->has_class() is available.
 		$this->assertStringNotContainsString( 'wp-caption', $output );
 		$this->assertStringNotContainsString( '<p class="wp-caption-text">', $output );
 
@@ -574,6 +607,7 @@ public function test_render_media() {
 			)
 		);
 		$output = ob_get_clean();
+		// @TODO: Update this test once $p->has_class() is available.
 		$this->assertStringContainsString( 'class="wp-caption alignnone"', $output );
 		$this->assertStringContainsString( '<p class="wp-caption-text">Default caption</p>', $output );
 
@@ -586,6 +620,7 @@ public function test_render_media() {
 			)
 		);
 		$output = ob_get_clean();
+		// @TODO: Update this test once $p->has_class() is available.
 		$this->assertStringContainsString( 'class="wp-caption alignnone"', $output );
 		$this->assertStringContainsString( '<p class="wp-caption-text">Custom caption</p>', $output );
 
@@ -601,6 +636,7 @@ public function test_render_media() {
 			)
 		);
 		$output = ob_get_clean();
+		// @TODO: Update this test once $p->has_class() is available.
 		$this->assertStringContainsString( 'style="width: 310px"', $output );
 		$this->assertStringContainsString( '<p class="wp-caption-text">Caption for an image with custom size</p>', $output );
 	}