diff --git a/bin/amphtml-update.py b/bin/amphtml-update.py
index 304d88917ea..24fca4d9e14 100755
--- a/bin/amphtml-update.py
+++ b/bin/amphtml-update.py
@@ -448,10 +448,12 @@ def GetTagSpec(tag_spec, attr_lists):
 			if isinstance(field_value, (unicode, str, bool, int)):
 				cdata_dict[ field_descriptor.name ] = field_value
 			elif isinstance( field_value, google.protobuf.pyext._message.RepeatedCompositeContainer ):
-				cdata_dict[ field_descriptor.name ] = {}
+				cdata_dict[ field_descriptor.name ] = []
 				for value in field_value:
+					entry = {}
 					for (key,val) in value.ListFields():
-						cdata_dict[ field_descriptor.name ][ key.name ] = val
+						entry[ key.name ] = val
+					cdata_dict[ field_descriptor.name ].append( entry )
 			elif hasattr( field_value, '_values' ):
 				cdata_dict[ field_descriptor.name ] = {}
 				for _value in field_value._values:
@@ -485,10 +487,11 @@ def GetTagSpec(tag_spec, attr_lists):
 				cdata_dict['css_spec'] = css_spec
 		if len( cdata_dict ) > 0:
 			if 'blacklisted_cdata_regex' in cdata_dict:
-				if 'error_message' not in cdata_dict['blacklisted_cdata_regex']:
-					raise Exception( 'Missing error_message for blacklisted_cdata_regex.' );
-				if cdata_dict['blacklisted_cdata_regex']['error_message'] not in ( 'CSS !important', 'contents', 'html comments', 'CSS i-amphtml- name prefix' ):
-					raise Exception( 'Unexpected error_message "%s" for blacklisted_cdata_regex.' % cdata_dict['blacklisted_cdata_regex']['error_message'] );
+				for entry in cdata_dict['blacklisted_cdata_regex']:
+					if 'error_message' not in entry:
+						raise Exception( 'Missing error_message for blacklisted_cdata_regex.' );
+					if entry['error_message'] not in ( 'contents', 'html comments', 'CSS i-amphtml- name prefix' ):
+						raise Exception( 'Unexpected error_message "%s" for blacklisted_cdata_regex.' % entry['error_message'] );
 			tag_spec_dict['cdata'] = cdata_dict
 
 	if 'spec_name' not in tag_spec_dict['tag_spec']:
diff --git a/includes/sanitizers/class-amp-allowed-tags-generated.php b/includes/sanitizers/class-amp-allowed-tags-generated.php
index b38591b8cfb..d4efb11d6a1 100644
--- a/includes/sanitizers/class-amp-allowed-tags-generated.php
+++ b/includes/sanitizers/class-amp-allowed-tags-generated.php
@@ -11960,8 +11960,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'contents',
-						'regex' => '.',
+						array(
+							'error_message' => 'contents',
+							'regex' => '.',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12001,8 +12003,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'contents',
-						'regex' => '.',
+						array(
+							'error_message' => 'contents',
+							'regex' => '.',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12026,8 +12030,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12053,8 +12059,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12075,8 +12083,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12293,8 +12303,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12501,8 +12513,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12587,8 +12601,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12762,8 +12778,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -12877,8 +12895,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 					'max_bytes' => 100000,
 					'max_bytes_spec_url' => 'https://amp.dev/documentation/components/amp-bind#state',
@@ -13146,8 +13166,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -13413,8 +13435,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 					'max_bytes' => 15000,
 					'max_bytes_spec_url' => 'https://amp.dev/documentation/components/amp-experiment#configuration',
@@ -13738,8 +13762,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -14334,8 +14360,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -14611,8 +14639,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -15183,8 +15213,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 					'max_bytes' => 10000,
 					'max_bytes_spec_url' => 'https://amp.dev/documentation/components/amp-script#faq',
@@ -15481,8 +15513,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -15557,8 +15591,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -15584,8 +15620,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 					'max_bytes' => 15000,
 					'max_bytes_spec_url' => 'https://amp.dev/documentation/components/amp-experiment#configuration',
@@ -15645,8 +15683,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -15734,8 +15774,10 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
 					),
 				),
 				'tag_spec' => array(
@@ -16626,8 +16668,14 @@ class AMP_Allowed_Tags_Generated {
 				),
 				'cdata' => array(
 					'blacklisted_cdata_regex' => array(
-						'error_message' => 'CSS i-amphtml- name prefix',
-						'regex' => '(^|\\W)i-amphtml-',
+						array(
+							'error_message' => 'html comments',
+							'regex' => '<!--',
+						),
+						array(
+							'error_message' => 'CSS i-amphtml- name prefix',
+							'regex' => '(^|\\W)i-amphtml-',
+						),
 					),
 					'css_spec' => array(
 						'allowed_at_rules' => array(
diff --git a/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php b/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
index 493c1472905..15b5d516e10 100644
--- a/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
+++ b/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
@@ -41,7 +41,7 @@ class AMP_Tag_And_Attribute_Sanitizer extends AMP_Base_Sanitizer {
 	const DUPLICATE_UNIQUE_TAG                 = 'DUPLICATE_UNIQUE_TAG';
 	const MANDATORY_CDATA_MISSING_OR_INCORRECT = 'MANDATORY_CDATA_MISSING_OR_INCORRECT';
 	const CDATA_TOO_LONG                       = 'CDATA_TOO_LONG';
-	const INVALID_CDATA_CSS_IMPORTANT          = 'INVALID_CDATA_CSS_IMPORTANT';
+	const INVALID_CDATA_CSS_I_AMPHTML_NAME     = 'INVALID_CDATA_CSS_I_AMPHTML_NAME';
 	const INVALID_CDATA_CONTENTS               = 'INVALID_CDATA_CONTENTS';
 	const INVALID_CDATA_HTML_COMMENTS          = 'INVALID_CDATA_HTML_COMMENTS';
 	const JSON_ERROR_CTRL_CHAR                 = 'JSON_ERROR_CTRL_CHAR';
@@ -919,21 +919,23 @@ private function validate_cdata_for_node( DOMElement $element, $cdata_spec ) {
 			];
 		}
 		if ( isset( $cdata_spec['blacklisted_cdata_regex'] ) ) {
-			if ( preg_match( '@' . $cdata_spec['blacklisted_cdata_regex']['regex'] . '@u', $element->textContent ) ) {
-				if ( isset( $cdata_spec['blacklisted_cdata_regex']['error_message'] ) ) {
-					// There are only a few error messages, so map them to error codes.
-					switch ( $cdata_spec['blacklisted_cdata_regex']['error_message'] ) {
-						case 'CSS !important':
-							return [ 'code' => self::INVALID_CDATA_CSS_IMPORTANT ];
-						case 'contents':
-							return [ 'code' => self::INVALID_CDATA_CONTENTS ];
-						case 'html comments':
-							return [ 'code' => self::INVALID_CDATA_HTML_COMMENTS ];
+			foreach ( $cdata_spec['blacklisted_cdata_regex'] as $blacklisted_cdata_regex ) {
+				if ( preg_match( '@' . $blacklisted_cdata_regex['regex'] . '@u', $element->textContent ) ) {
+					if ( isset( $blacklisted_cdata_regex['error_message'] ) ) {
+						// There are only a few error messages, so map them to error codes.
+						switch ( $blacklisted_cdata_regex['error_message'] ) {
+							case 'CSS i-amphtml- name prefix':
+								return [ 'code' => self::INVALID_CDATA_CSS_I_AMPHTML_NAME ]; // @todo This really should be done as part of the CSS sanitizer.
+							case 'contents':
+								return [ 'code' => self::INVALID_CDATA_CONTENTS ];
+							case 'html comments':
+								return [ 'code' => self::INVALID_CDATA_HTML_COMMENTS ];
+						}
 					}
-				}
 
-				// Note: This fallback case is not currently reachable because all error messages are accounted for in the switch statement.
-				return [ 'code' => self::CDATA_VIOLATES_BLACKLIST ];
+					// Note: This fallback case is not currently reachable because all error messages are accounted for in the switch statement.
+					return [ 'code' => self::CDATA_VIOLATES_BLACKLIST ];
+				}
 			}
 		} elseif ( isset( $cdata_spec['cdata_regex'] ) ) {
 			$delimiter = false === strpos( $cdata_spec['cdata_regex'], '@' ) ? '@' : '#';
diff --git a/includes/validation/class-amp-validation-error-taxonomy.php b/includes/validation/class-amp-validation-error-taxonomy.php
index 8a6501b67cd..ae2e704d461 100644
--- a/includes/validation/class-amp-validation-error-taxonomy.php
+++ b/includes/validation/class-amp-validation-error-taxonomy.php
@@ -3042,7 +3042,7 @@ public static function get_error_title_from_code( $validation_error ) {
 			case AMP_Tag_And_Attribute_Sanitizer::CDATA_TOO_LONG:
 			case AMP_Tag_And_Attribute_Sanitizer::MANDATORY_CDATA_MISSING_OR_INCORRECT:
 			case AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_HTML_COMMENTS:
-			case AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_CSS_IMPORTANT:
+			case AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_CSS_I_AMPHTML_NAME:
 			case AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_CONTENTS:
 			case AMP_Tag_And_Attribute_Sanitizer::CDATA_VIOLATES_BLACKLIST:
 				return esc_html__( 'Illegal text content', 'amp' );
diff --git a/tests/php/test-tag-and-attribute-sanitizer.php b/tests/php/test-tag-and-attribute-sanitizer.php
index 6cecad56d75..8b64c7f32dc 100644
--- a/tests/php/test-tag-and-attribute-sanitizer.php
+++ b/tests/php/test-tag-and-attribute-sanitizer.php
@@ -2907,11 +2907,17 @@ public function get_html_data() {
 					],
 				],
 			],
-			'cdata_css_important'                     => [
-				'<html amp><head><meta charset="utf-8"><style amp-custom>body { outline: solid 1px red !important; }</style></head><body></body></html>',
+			'cdata_css_i_amphtml_name'                => [
+				'<html amp><head><meta charset="utf-8"><style amp-custom>i-amphtml-scroll-container { outline: solid 1px red; }</style></head><body></body></html>',
 				'<html amp><head><meta charset="utf-8"></head><body></body></html>',
 				[],
-				[ AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_CSS_IMPORTANT ],
+				[ AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_CSS_I_AMPHTML_NAME ],
+			],
+			'cdata_css_html_comment'                  => [
+				'<html amp><head><meta charset="utf-8"><style amp-custom>/* <!-- not good --> */</style></head><body></body></html>',
+				'<html amp><head><meta charset="utf-8"></head><body></body></html>',
+				[],
+				[ AMP_Tag_And_Attribute_Sanitizer::INVALID_CDATA_HTML_COMMENTS ],
 			],
 			'cdata_contents_bad_comment'              => [
 				'<html><head><meta charset="utf-8"><script type="application/ld+json"><!--{"@context":"http:\/\/schema.org"}--></script></head><body></body></html>',