diff --git a/bin/amphtml-update.py b/bin/amphtml-update.py
index 00f40e338b5..f9ddb389312 100755
--- a/bin/amphtml-update.py
+++ b/bin/amphtml-update.py
@@ -24,7 +24,7 @@
 import collections
 import json
 import google
-import imp
+from collections.abc import Sequence
 
 seen_spec_names = set()
 
@@ -38,49 +38,57 @@ def Die(msg):
 
 def SetupOutDir(out_dir):
 	"""Sets up a clean output directory.
-
 	Args:
-		out_dir: directory name of the output directory.
+	  out_dir: directory name of the output directory. Must not have slashes,
+		dots, etc.
 	"""
+	logging.info('entering ...')
+	assert re.match(r'^[a-zA-Z_\-0-9]+$', out_dir), 'bad out_dir: %s' % out_dir
 
 	if os.path.exists(out_dir):
 		subprocess.check_call(['rm', '-rf', out_dir])
 	os.mkdir(out_dir)
+	logging.info('... done')
 
 
 def GenValidatorPb2Py(validator_directory, out_dir):
 	"""Calls the proto compiler to generate validator_pb2.py.
-
 	Args:
-		validator_directory: directory name of the validator.
-		out_dir: directory name of the output directory.
+	  out_dir: directory name of the output directory. Must not have slashes,
+		dots, etc.
 	"""
+	logging.info('entering ...')
+	assert re.match(r'^[a-zA-Z_\-0-9]+$', out_dir), 'bad out_dir: %s' % out_dir
 
-	os.chdir( validator_directory )
-	subprocess.check_call(['protoc', 'validator.proto', '--python_out=%s' % out_dir])
-	os.chdir( out_dir )
-	open('__init__.py', 'w').close()
+	subprocess.check_call(
+		['protoc', os.path.join(validator_directory, 'validator.proto'), '--proto_path=%s' % validator_directory, '--python_out=%s' % out_dir])
+	open('%s/__init__.py' % out_dir, 'w').close()
+	logging.info('... done')
 
 def GenValidatorProtoascii(validator_directory, out_dir):
 	"""Assembles the validator protoascii file from the main and extensions.
-
 	Args:
-		validator_directory: directory for where the validator is located, inside the amphtml repo.
-		out_dir: directory name of the output directory.
+	  out_dir: directory name of the output directory. Must not have slashes,
+		dots, etc.
 	"""
-
-	protoascii_segments = [
-		open(os.path.join(validator_directory, 'validator-main.protoascii')).read(),
-		open(os.path.join(validator_directory, 'validator-svg.protoascii')).read(),
-		open(os.path.join(validator_directory, 'validator-css.protoascii')).read()
-	]
-	extensions = glob.glob(os.path.join(validator_directory, '../extensions/*/validator-*.protoascii'))
+	logging.info('entering ...')
+	assert re.match(r'^[a-zA-Z_\-0-9]+$', out_dir), 'bad out_dir: %s' % out_dir
+
+	protoascii_segments = [open(os.path.join(validator_directory, 'validator-main.protoascii')).read()]
+	protoascii_segments.append(open(os.path.join(validator_directory, 'validator-css.protoascii')).read())
+	protoascii_segments.append(open(os.path.join(validator_directory, 'validator-svg.protoascii')).read())
+	extensions = glob.glob(os.path.join(validator_directory, 'extensions/*/validator-*.protoascii'))
+	# In the Github project, the extensions are located in a sibling directory
+	# to the validator rather than a child directory.
+	if not extensions:
+		extensions = glob.glob(os.path.join(validator_directory, '../extensions/*/validator-*.protoascii'))
 	extensions.sort()
 	for extension in extensions:
 		protoascii_segments.append(open(extension).read())
 	f = open('%s/validator.protoascii' % out_dir, 'w')
 	f.write(''.join(protoascii_segments))
 	f.close()
+	logging.info('... done')
 
 
 def GeneratePHP(repo_directory, out_dir):
@@ -94,8 +102,8 @@ def GeneratePHP(repo_directory, out_dir):
 	allowed_tags, attr_lists, descendant_lists, reference_points, versions = ParseRules(repo_directory, out_dir)
 
 	expected_spec_names = (
-		'style amp-custom',
-		'style[amp-keyframes]',
+		b'style amp-custom',
+		b'style[amp-keyframes]',
 	)
 	for expected_spec_name in expected_spec_names:
 		if expected_spec_name not in seen_spec_names:
@@ -120,7 +128,7 @@ def GeneratePHP(repo_directory, out_dir):
 	output = re.sub("'False'", "false", output)
 
 	# Write the php file to STDOUT.
-	print output
+	print( output )
 
 def GenerateHeaderPHP(out):
 	# Output the file's header
@@ -163,14 +171,14 @@ def GenerateAllowedTagsPHP(out, allowed_tags):
 def GenerateLayoutAttributesPHP(out, attr_lists):
 	# Output the attribute list allowed for layouts.
 	out.append('')
-	out.append('\tprivate static $layout_allowed_attrs = %s;' % Phpize( attr_lists['$AMP_LAYOUT_ATTRS'], 1 ).lstrip() )
+	out.append('\tprivate static $layout_allowed_attrs = %s;' % Phpize( attr_lists[b'$AMP_LAYOUT_ATTRS'], 1 ).lstrip() )
 	out.append('')
 
 
 def GenerateGlobalAttributesPHP(out, attr_lists):
 	# Output the globally allowed attribute list.
 	out.append('')
-	out.append('\tprivate static $globally_allowed_attrs = %s;' % Phpize( attr_lists['$GLOBAL_ATTRS'], 1 ).lstrip() )
+	out.append('\tprivate static $globally_allowed_attrs = %s;' % Phpize( attr_lists[b'$GLOBAL_ATTRS'], 1 ).lstrip() )
 	out.append('')
 
 def GenerateReferencePointsPHP(out, reference_points):
@@ -301,9 +309,14 @@ def ParseRules(repo_directory, out_dir):
 	# These imports happen late, within this method because they don't necessarily
 	# exist when the module starts running, and the ones that probably do
 	# are checked by CheckPrereqs.
+	# pylint: disable=g-import-not-at-top
 
 	from google.protobuf import text_format
-	validator_pb2 = imp.load_source('validator_pb2', os.path.join( out_dir, 'validator_pb2.py' ))
+	from google.protobuf import json_format
+	from google.protobuf import descriptor
+
+	sys.path.append(os.getcwd())
+	from amp_validator_dist import validator_pb2
 
 	allowed_tags = {}
 	attr_lists = {}
@@ -361,15 +374,16 @@ def ParseRules(repo_directory, out_dir):
 					continue
 
 				# If we made it here, then start adding the tag_spec
-				if tag_spec.tag_name.lower() not in allowed_tags:
+				tag_name = tag_spec.tag_name.lower()
+				if tag_name not in allowed_tags:
 					tag_list = []
 				else:
-					tag_list = allowed_tags[UnicodeEscape(tag_spec.tag_name).lower()]
+					tag_list = allowed_tags[tag_name]
 
 				gotten_tag_spec = GetTagSpec(tag_spec, attr_lists)
 				if gotten_tag_spec is not None:
 					tag_list.append(gotten_tag_spec)
-					allowed_tags[UnicodeEscape(tag_spec.tag_name).lower()] = tag_list
+					allowed_tags[tag_name] = tag_list
 		elif 'descendant_tag_list' == field_desc.name:
 			for _list in field_val:
 				descendant_lists[_list.name] = []
@@ -517,7 +531,7 @@ def ParseRules(repo_directory, out_dir):
 			# Remove redundant information.
 			del extension_script_list[0]['tag_spec']['extension_spec']['bento_supported_version']
 
-		validator_versions = sorted( validator_versions, key=lambda version: map(int, version.split('.') ) )
+		validator_versions = sorted( validator_versions, key=lambda version: list(map(int, version.split('.') )) )
 		extension_script_list[0]['tag_spec']['extension_spec']['version'] = validator_versions
 
 		if 'bento' in extensions_versions[extension_name] and extensions_versions[extension_name]['bento']['version'] in validator_versions:
@@ -593,7 +607,7 @@ def GetTagSpec(tag_spec, attr_lists):
 	if tag_spec.HasField('cdata'):
 		cdata_dict = {}
 		for (field_descriptor, field_value) in tag_spec.cdata.ListFields():
-			if isinstance(field_value, (unicode, str, bool, int)):
+			if isinstance(field_value, (str, bytes, bool, int)):
 				cdata_dict[ field_descriptor.name ] = field_value
 			elif isinstance( field_value, google.protobuf.pyext._message.RepeatedCompositeContainer ):
 				cdata_dict[ field_descriptor.name ] = []
@@ -620,12 +634,12 @@ def GetTagSpec(tag_spec, attr_lists):
 					if not hasattr( field_value, css_spec_field_name ):
 						continue
 					css_spec_field_value = getattr( field_value, css_spec_field_name )
-					if isinstance(css_spec_field_value, (list, collections.Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
+					if isinstance(css_spec_field_value, (list, Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
 						css_spec[ css_spec_field_name ] = [ val for val in css_spec_field_value ]
 					elif hasattr( css_spec_field_value, 'ListFields' ):
 						css_spec[ css_spec_field_name ] = {}
 						for (css_spec_field_item_descriptor, css_spec_field_item_value) in getattr( field_value, css_spec_field_name ).ListFields():
-							if isinstance(css_spec_field_item_value, (list, collections.Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
+							if isinstance(css_spec_field_item_value, (list, Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
 								css_spec[ css_spec_field_name ][ css_spec_field_item_descriptor.name ] = [ val for val in css_spec_field_item_value ]
 							else:
 								css_spec[ css_spec_field_name ][ css_spec_field_item_descriptor.name ] = css_spec_field_item_value
@@ -715,7 +729,7 @@ def GetTagRules(tag_spec):
 
 	# Ignore amp-custom-length-check because the AMP plugin will indicate how close they are to the limit.
 	# TODO: Remove the AMP4EMAIL check once this change is released: <https://github.com/ampproject/amphtml/pull/25246>.
-	if tag_spec.HasField('spec_name') and ( str(tag_spec.spec_name) == 'style amp-custom-length-check' or 'AMP4EMAIL' in str(tag_spec.spec_name) ):
+	if tag_spec.HasField('spec_name') and ( tag_spec.spec_name == 'style amp-custom-length-check' or 'AMP4EMAIL' in tag_spec.spec_name ):
 		return None
 
 	if tag_spec.HasField('extension_spec'):
@@ -892,7 +906,7 @@ def GetValues(attr_spec):
 				# print 'value_property.name: %s' % value_property.name
 				for (key,val) in value_property.ListFields():
 					if val != value_property.name:
-						if isinstance(val, unicode):
+						if isinstance(val, str):
 							val = UnicodeEscape(val)
 						property_dict[UnicodeEscape(key.name)] = val
 				value_properties_dict[UnicodeEscape(value_property.name)] = property_dict
@@ -902,7 +916,7 @@ def GetValues(attr_spec):
 	if attr_spec.HasField('value_url'):
 		value_url_dict = {}
 		for (value_url_key, value_url_val) in attr_spec.value_url.ListFields():
-			if isinstance(value_url_val, (list, collections.Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
+			if isinstance(value_url_val, (list, Sequence, google.protobuf.internal.containers.RepeatedScalarFieldContainer, google.protobuf.pyext._message.RepeatedScalarContainer)):
 				value_url_val_val = []
 				for val in value_url_val:
 					value_url_val_val.append(UnicodeEscape(val))
@@ -956,6 +970,23 @@ def GetMandatoryOf( attr, constraint ):
 
 	return sorted(attributes)
 
+def to_json(data):
+	"""Make data JSON-serializable
+
+	Hat tip to AYHarano via https://stackoverflow.com/a/44060541/93579
+	"""
+	if data is None or isinstance(data, (bool, int, str)):
+		return data
+	if isinstance( data, bytes ):
+		return data.decode('utf8')
+	if isinstance( data, (tuple, range, list) ):
+		return [to_json(item) for item in data]
+	if isinstance(data, (set, frozenset)):
+		return sorted(data)
+	if isinstance(data, (dict, collections.defaultdict)):
+		return {to_json(key): to_json(data[key]) for key in data}
+	raise TypeError
+
 def Phpize(data, indent=0):
 	"""Helper function to convert JSON-serializable data into PHP literals.
 
@@ -964,10 +995,10 @@ def Phpize(data, indent=0):
 	Returns:
 		String formatted as PHP literal.
 	"""
-	json_string = json.dumps(data, sort_keys=True, ensure_ascii=False)
+	json_string = json.dumps(to_json(data), sort_keys=True, ensure_ascii=False)
 
 	pipe = subprocess.Popen(['php', '-r', 'var_export( json_decode( file_get_contents( "php://stdin" ), true ) );'], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.STDOUT)
-	php_stdout = pipe.communicate(input=json_string)[0]
+	php_stdout = pipe.communicate(input=bytes(json_string, 'utf8'))[0]
 	php_exported = php_stdout.decode()
 
 	# Clean up formatting.
@@ -987,12 +1018,10 @@ def Main( repo_directory, out_dir ):
 	logging.basicConfig(format='[[%(filename)s %(funcName)s]] - %(message)s', level=logging.INFO)
 
 	validator_directory = os.path.realpath( os.path.join( repo_directory, 'validator' ) )
-	out_dir = os.path.realpath(out_dir)
 
 	SetupOutDir(out_dir)
 	GenValidatorProtoascii(validator_directory, out_dir)
 	GenValidatorPb2Py(validator_directory, out_dir)
-	GenValidatorProtoascii(validator_directory,out_dir)
 	GeneratePHP(repo_directory, out_dir)
 
 if __name__ == '__main__':
@@ -1002,5 +1031,5 @@ def Main( repo_directory, out_dir ):
 	if not os.path.exists( repo_directory ):
 		Die( "Error: The amphtml directory does not exist: %s" % validator_directory )
 	repo_directory = os.path.realpath( repo_directory )
-	out_dir = os.path.join( tempfile.gettempdir(), 'amp_wp' )
-	Main( repo_directory, out_dir )
+	os.chdir( tempfile.gettempdir() )
+	Main( repo_directory, 'amp_validator_dist' )
diff --git a/bin/amphtml-update.sh b/bin/amphtml-update.sh
index 4709f711748..9c5e7eb1d8a 100755
--- a/bin/amphtml-update.sh
+++ b/bin/amphtml-update.sh
@@ -17,11 +17,11 @@ BIN_PATH="$(dirname "$0")"
 PROJECT_PATH=$(dirname $BIN_PATH)
 AMPHTML_LOCATION="$1"
 
-if ! command -v python >/dev/null 2>&1 || ! python -c "import google.protobuf" 2>/dev/null; then
+if ! command -v python3 >/dev/null 2>&1 || ! python3 -c "import google.protobuf" 2>/dev/null; then
 	echo "Error: The google.protobuf Python module is not installed."
 	echo
 	echo "On Linux, you can install the required dependencies via:"
-	echo "# apt-get install python protobuf-compiler python-protobuf"
+	echo "# apt-get install python3 protobuf-compiler python3-protobuf"
 	echo
 	echo "On MacOS, Python is already installed but you may install via:"
 	echo "$ pip install --upgrade protobuf"
@@ -52,7 +52,7 @@ else
 fi
 
 # Run script.
-python "$BIN_PATH/amphtml-update.py" "$AMPHTML_LOCATION" > "$PROJECT_PATH/includes/sanitizers/class-amp-allowed-tags-generated.php"
+python3 "$BIN_PATH/amphtml-update.py" "$AMPHTML_LOCATION" > "$PROJECT_PATH/includes/sanitizers/class-amp-allowed-tags-generated.php"
 
 if [[ $CLEANUP == 1 ]]; then
 	rm -r "$AMPHTML_LOCATION"
diff --git a/includes/sanitizers/class-amp-allowed-tags-generated.php b/includes/sanitizers/class-amp-allowed-tags-generated.php
index ecf35123d73..45b87352fb9 100644
--- a/includes/sanitizers/class-amp-allowed-tags-generated.php
+++ b/includes/sanitizers/class-amp-allowed-tags-generated.php
@@ -272,6 +272,7 @@ class AMP_Allowed_Tags_Generated {
 			'amp-story-interactive-quiz',
 			'amp-story-interactive-results',
 			'amp-story-panning-media',
+			'amp-story-shopping-tag',
 			'amp-timeago',
 			'amp-twitter',
 			'amp-video',
@@ -1409,6 +1410,7 @@ class AMP_Allowed_Tags_Generated {
 						'supported_layouts' => array(
 							2,
 							3,
+							5,
 							1,
 						),
 					),
@@ -6363,6 +6365,12 @@ class AMP_Allowed_Tags_Generated {
 							'',
 						),
 					),
+					'style-preset' => array(
+						'value' => array(
+							'default',
+							'appear',
+						),
+					),
 				),
 				'tag_spec' => array(
 					'amp_layout' => array(
@@ -6942,6 +6950,7 @@ class AMP_Allowed_Tags_Generated {
 							'amp-story-grid-layer',
 							'amp-story-page-attachment',
 							'amp-story-page-outlink',
+							'amp-story-shopping-attachment',
 						),
 						'mandatory_min_num_child_tags' => 1,
 					),
@@ -7134,42 +7143,34 @@ class AMP_Allowed_Tags_Generated {
 		'amp-story-shopping-attachment' => array(
 			array(
 				'attr_spec_list' => array(
-					'media' => array(),
-					'noloading' => array(
-						'value' => array(
-							'',
-						),
-					),
-				),
-				'tag_spec' => array(
-					'amp_layout' => array(
-						'supported_layouts' => array(
-							1,
+					'cta-text' => array(),
+					'src' => array(
+						'value_url' => array(
+							'allow_relative' => true,
+							'protocol' => array(
+								'https',
+							),
 						),
 					),
-					'requires_extension' => array(
-						'amp-story-shopping',
-					),
-					'spec_url' => 'https://amp.dev/documentation/components/amp-story-shopping/',
-				),
-			),
-		),
-		'amp-story-shopping-config' => array(
-			array(
-				'attr_spec_list' => array(
-					'media' => array(),
-					'noloading' => array(
+					'theme' => array(
 						'value' => array(
-							'',
+							'dark',
+							'light',
 						),
 					),
 				),
 				'tag_spec' => array(
 					'amp_layout' => array(
 						'supported_layouts' => array(
-							1,
+							5,
 						),
 					),
+					'child_tags' => array(
+						'child_tag_name_oneof' => array(
+							'script',
+						),
+						'mandatory_min_num_child_tags' => 1,
+					),
 					'requires_extension' => array(
 						'amp-story-shopping',
 					),
@@ -7180,11 +7181,8 @@ class AMP_Allowed_Tags_Generated {
 		'amp-story-shopping-tag' => array(
 			array(
 				'attr_spec_list' => array(
-					'media' => array(),
-					'noloading' => array(
-						'value' => array(
-							'',
-						),
+					'data-product-id' => array(
+						'mandatory' => true,
 					),
 				),
 				'tag_spec' => array(
@@ -7896,7 +7894,7 @@ class AMP_Allowed_Tags_Generated {
 						),
 					),
 					'volume' => array(
-						'value_regex' => '^((0?\\.[1-9]+)?|1(\\.0*)?)$',
+						'value_regex' => '^(0(\\.0*)?|(0?\\.[0-9]+)?|1(\\.0*)?)$',
 					),
 				),
 				'tag_spec' => array(
@@ -8413,6 +8411,16 @@ class AMP_Allowed_Tags_Generated {
 					'spec_url' => 'https://amp.dev/documentation/components/amp-audio/',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'controls' => array(),
+				),
+				'tag_spec' => array(
+					'mandatory_ancestor' => 'amp-audio',
+					'spec_name' => 'amp-audio > audio',
+					'spec_url' => 'https://amp.dev/documentation/components/amp-audio/',
+				),
+			),
 		),
 		'b' => array(
 			array(
@@ -15669,6 +15677,34 @@ class AMP_Allowed_Tags_Generated {
 					'spec_url' => 'https://amp.dev/documentation/components/amp-story-auto-ads/',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'nonce' => array(),
+					'type' => array(
+						'dispatch_key' => 3,
+						'mandatory' => true,
+						'value_casei' => array(
+							'application/json',
+						),
+					),
+				),
+				'cdata' => array(
+					'disallowed_cdata_regex' => array(
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-story-shopping-attachment',
+					'requires_extension' => array(
+						'amp-story-shopping',
+					),
+					'spec_name' => 'amp-story-shopping-attachment config script',
+					'spec_url' => 'https://amp.dev/documentation/components/amp-story-shopping/',
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'nonce' => array(),
@@ -16445,11 +16481,16 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'tag_spec' => array(
 					'extension_spec' => array(
+						'bento' => array(
+							'has_css' => false,
+							'version' => '1.0',
+						),
 						'latest' => '0.1',
 						'name' => 'amp-audio',
 						'requires_usage' => true,
 						'version' => array(
 							'0.1',
+							'1.0',
 						),
 					),
 				),
@@ -22903,6 +22944,9 @@ class AMP_Allowed_Tags_Generated {
 				'animate-in-delay' => array(),
 				'animate-in-duration' => array(),
 				'animate-in-timing-function' => array(),
+				'pan-scaling-factor' => array(
+					'value_regex_casei' => '^([0-9]*[.]?[0-9]+)|([0-9]+[.]?[0-9]*)$',
+				),
 				'scale-end' => array(
 					'value_regex' => '[0-9]+([.][0-9]+)?',
 				),
@@ -22971,6 +23015,9 @@ class AMP_Allowed_Tags_Generated {
 						'',
 					),
 				),
+				'pan-scaling-factor' => array(
+					'value_regex_casei' => '^([0-9]*[.]?[0-9]+)|([0-9]+[.]?[0-9]*)$',
+				),
 				'scale-end' => array(
 					'value_regex' => '[0-9]+([.][0-9]+)?',
 				),
@@ -23099,6 +23146,9 @@ class AMP_Allowed_Tags_Generated {
 						'stretch',
 					),
 				),
+				'pan-scaling-factor' => array(
+					'value_regex_casei' => '^([0-9]*[.]?[0-9]+)|([0-9]+[.]?[0-9]*)$',
+				),
 				'scale-end' => array(
 					'value_regex' => '[0-9]+([.][0-9]+)?',
 				),
diff --git a/tests/php/test-amp-helper-functions.php b/tests/php/test-amp-helper-functions.php
index d21f34cc3e4..9b0f7fe5c0d 100644
--- a/tests/php/test-amp-helper-functions.php
+++ b/tests/php/test-amp-helper-functions.php
@@ -1591,7 +1591,7 @@ public function test_amp_register_default_scripts_and_styles_with_bento() {
 			'amp-animation'                => 'v0/amp-animation-0.1.js',
 			'amp-apester-media'            => 'v0/amp-apester-media-0.1.js',
 			'amp-app-banner'               => 'v0/amp-app-banner-0.1.js',
-			'amp-audio'                    => 'v0/amp-audio-0.1.js',
+			'amp-audio'                    => 'v0/amp-audio-1.0.js',
 			'amp-auto-ads'                 => 'v0/amp-auto-ads-0.1.js',
 			'amp-autocomplete'             => 'v0/amp-autocomplete-0.1.js',
 			'amp-base-carousel'            => 'v0/amp-base-carousel-1.0.js',
diff --git a/tests/php/validation/test-class-amp-validation-manager.php b/tests/php/validation/test-class-amp-validation-manager.php
index ee2db4fe4fd..e222e5d1386 100644
--- a/tests/php/validation/test-class-amp-validation-manager.php
+++ b/tests/php/validation/test-class-amp-validation-manager.php
@@ -1338,7 +1338,7 @@ public function get_block_data() {
 			'latest_posts' => [
 				'<!-- wp:latest-posts {"postsToShow":1} /-->',
 				sprintf(
-					'<!--amp-source-stack {"block_name":"core\/latest-posts","post_id":{{post_id}},"block_content_index":0,"block_attrs":{"postsToShow":1},"type":"%1$s","name":"%2$s","file":%4$s,"line":%5$s,"function":"%3$s"}--><ul class="%6$s"><li><a href="{{url}}">{{title}}</a></li></ul><!--/amp-source-stack {"block_name":"core\/latest-posts","post_id":{{post_id}},"block_attrs":{"postsToShow":1},"type":"%1$s","name":"%2$s","file":%4$s,"line":%5$s,"function":"%3$s"}-->',
+					'<!--amp-source-stack {"block_name":"core\/latest-posts","post_id":{{post_id}},"block_content_index":0,"block_attrs":{"postsToShow":1},"type":"%1$s","name":"%2$s","file":%4$s,"line":%5$s,"function":"%3$s"}--><ul class="wp-block-latest-posts wp-block-latest-posts__list"><li><a href="{{url}}">{{title}}</a></li></ul><!--/amp-source-stack {"block_name":"core\/latest-posts","post_id":{{post_id}},"block_attrs":{"postsToShow":1},"type":"%1$s","name":"%2$s","file":%4$s,"line":%5$s,"function":"%3$s"}-->',
 					$is_gutenberg ? 'plugin' : 'core',
 					$is_gutenberg ? 'gutenberg' : 'wp-includes',
 					$latest_posts_block->render_callback instanceof Closure ? '{closure}' : $latest_posts_block->render_callback,
@@ -1347,10 +1347,7 @@ public function get_block_data() {
 						? preg_replace( ':.*gutenberg/:', '', $reflection_function->getFileName() )
 						: preg_replace( ':.*wp-includes/:', '', $reflection_function->getFileName() )
 					),
-					$reflection_function->getStartLine(),
-					( defined( 'GUTENBERG_DEVELOPMENT_MODE' ) || defined( 'GUTENBERG_VERSION' ) && GUTENBERG_VERSION && version_compare( GUTENBERG_VERSION, '8.8.0', '>=' ) )
-						? 'wp-block-latest-posts__list wp-block-latest-posts'
-						: 'wp-block-latest-posts wp-block-latest-posts__list'
+					$reflection_function->getStartLine()
 				),
 				[
 					'element' => 'ul',
@@ -1416,6 +1413,13 @@ public function test_add_block_source_comments( $content, $expected, $query ) {
 		// Remove class added in <https://github.com/WordPress/gutenberg/pull/38740> to normalize with expected data.
 		$rendered_block = str_replace( ' class="wp-block-latest-posts__post-title"', '', $rendered_block );
 
+		// Normalize class ordering.
+		$rendered_block = str_replace(
+			'wp-block-latest-posts__list wp-block-latest-posts',
+			'wp-block-latest-posts wp-block-latest-posts__list',
+			$rendered_block
+		);
+
 		$this->assertEquals(
 			preg_replace( '/(?<=>)\s+(?=<)/', '', str_replace( '%d', $post->ID, $expected ) ),
 			preg_replace( '/(?<=>)\s+(?=<)/', '', $rendered_block )