A new class file which will override Blacklist Sanitizer

Override Blacklist sanitizer

<?php
$amp_blacklist_sanitizer = realpath( AMP__VENDOR__DIR__  . '/includes/sanitizers/class-amp-blacklist-sanitizer.php' );
if ( $amp_blacklist_sanitizer ) {
	include_once $amp_blacklist_sanitizer;
}
if ( class_exists( 'AMPforWP\\AMPVendor\\AMP_Blacklist_Sanitizer' ) ) {
	class AMP_New_Blacklist extends AMPforWP\AMPVendor\AMP_Blacklist_Sanitizer {
		const PATTERN_REL_WP_ATTACHMENT = '#wp-att-([\d]+)#';

		protected $DEFAULT_ARGS = array(
			'add_blacklisted_protocols' => array(),
			'add_blacklisted_tags' => array(),
			'add_blacklisted_attributes' => array(),
		);

		public function sanitize() {
			$blacklisted_tags = $this->get_blacklisted_tags();
			$blacklisted_attributes = $this->get_blacklisted_attributes();
			$blacklisted_protocols = $this->get_blacklisted_protocols();
			$body = $this->get_body_node();
			$this->strip_tags( $body, $blacklisted_tags );
			$this->strip_attributes_recursive( $body, $blacklisted_attributes, $blacklisted_protocols );
		}
		
		private function strip_attributes_recursive( $node, $bad_attributes, $bad_protocols ) {
			if ( $node->nodeType !== XML_ELEMENT_NODE ) {
				return;
			}

			$node_name = $node->nodeName;

			// Some nodes may contain valid content but are themselves invalid.
			// Remove the node but preserve the children.
	 		if ( 'font' === $node_name ) {
				$this->replace_node_with_children( $node, $bad_attributes, $bad_protocols );
				return;
			} elseif ( 'a' === $node_name && false === $this->validate_a_node( $node ) ) {
				$this->replace_node_with_children( $node, $bad_attributes, $bad_protocols );
				return;
			}

			if ( $node->hasAttributes() ) {
				$length = $node->attributes->length;
				for ( $i = $length - 1; $i >= 0; $i-- ) {
					$attribute = $node->attributes->item( $i );
					$attribute_name = strtolower( $attribute->name );
					if ( in_array( $attribute_name, $bad_attributes ) ) {
						$node->removeAttribute( $attribute_name );
						continue;
					}

					// on* attributes (like onclick) are a special case
					if ( 0 === stripos( $attribute_name, 'on' ) && $attribute_name != 'on' ) {
						$node->removeAttribute( $attribute_name );
						continue;
					} elseif ( 'a' === $node_name ) {
						$this->sanitize_a_attribute( $node, $attribute );
					}
				}
			}

			$length = $node->childNodes->length;
			for ( $i = $length - 1; $i >= 0; $i-- ) {
				$child_node = $node->childNodes->item( $i );

				$this->strip_attributes_recursive( $child_node, $bad_attributes, $bad_protocols );
			}
		}
		
		private function strip_tags( $node, $tag_names ) {
			foreach ( $tag_names as $tag_name ) {
				$elements = $node->getElementsByTagName( $tag_name );
				$length = $elements->length;
				if ( 0 === $length ) {
					continue;
				}

				for ( $i = $length - 1; $i >= 0; $i-- ) {
					$element = $elements->item( $i );
					$parent_node = $element->parentNode;
					$parent_node->removeChild( $element );

					if ( 'body' !== $parent_node->nodeName && AMP_DOM_Utils::is_node_empty( $parent_node ) ) {
						$parent_node->parentNode->removeChild( $parent_node );
					}
				}
			}
		}

		private function sanitize_a_attribute( $node, $attribute ) {
			$attribute_name = strtolower( $attribute->name );

			if ( 'rel' === $attribute_name ) {
				$old_value = $attribute->value;
				$new_value = trim( preg_replace( self::PATTERN_REL_WP_ATTACHMENT, '', $old_value ) );
				if ( empty( $new_value ) ) {
					$node->removeAttribute( $attribute_name );
				} elseif ( $old_value !== $new_value ) {
					$node->setAttribute( $attribute_name, $new_value );
				}
			} elseif ( 'rev' === $attribute_name ) {
				// rev removed from HTML5 spec, which was used by Jetpack Markdown.
				$node->removeAttribute( $attribute_name );
			} elseif ( 'target' === $attribute_name ) {
				// _blank is the only allowed value and it must be lowercase.
				// replace _new with _blank and others should simply be removed.
				$old_value = strtolower( $attribute->value );
				if ( '_blank' === $old_value || '_new' === $old_value ) {
					// _new is not allowed; swap with _blank
					$node->setAttribute( $attribute_name, '_blank' );
				} else {
					// only _blank is allowed
					$node->removeAttribute( $attribute_name );
				}
			}
		}

		private function validate_a_node( $node ) {
			// Get the href attribute
			$href = $node->getAttribute( 'href' );

			// If no href is set and this isn't an anchor, it's invalid
			if ( empty( $href ) ) {
				$name_attr = $node->getAttribute( 'name' );
				if ( ! empty( $name_attr ) ) {
					// No further validation is required
					return true;
				} else {
					return false;
				}
			}

			// If this is an anchor link, just return true
			if ( 0 === strpos( $href, '#' ) ) {
				return true;
			}

			// If the href starts with a '/', append the home_url to it for validation purposes.
			if ( 0 === stripos( $href, '/' ) ) {
				$href = untrailingslashit( get_home_url() ) . $href;
			}

			$valid_protocols = array( 'http', 'https', 'mailto', 'sms', 'tel', 'viber', 'whatsapp' );
			$special_protocols = array( 'tel', 'sms' ); // these ones don't valid with `filter_var+FILTER_VALIDATE_URL`
			$protocol = strtok( $href, ':' );

			if ( false === filter_var( $href, FILTER_VALIDATE_URL )
				&& ! in_array( $protocol, $special_protocols ) ) {
				return false;
			}

			if ( ! in_array( $protocol, $valid_protocols ) ) {
				return false;
			}

			return true;
		}

		private function replace_node_with_children( $node, $bad_attributes, $bad_protocols ) {
			// If the node has children and also has a parent node,
			// clone and re-add all the children just before current node.
			if ( $node->hasChildNodes() && $node->parentNode ) {
				foreach ( $node->childNodes as $child_node ) {
					$new_child = $child_node->cloneNode( true );
					$this->strip_attributes_recursive( $new_child, $bad_attributes, $bad_protocols );
					$node->parentNode->insertBefore( $new_child, $node );
				}
			}

			// Remove the node from the parent, if defined.
			if ( $node->parentNode ) {
				$node->parentNode->removeChild( $node );
			}
		}

		private function merge_defaults_with_args( $key, $values ) {
			// Merge default values with user specified args
			if ( ! empty( $this->args[ $key ] )
				&& is_array( $this->args[ $key ] ) ) {
				$values = array_merge( $values, $this->args[ $key ] );
			}

			return $values;
		}

		private function get_blacklisted_protocols() {
			return $this->merge_defaults_with_args( 'add_blacklisted_protocols', array(
				'javascript',
			) );
		}
		
		private function get_blacklisted_tags() {
			return $this->merge_defaults_with_args( 'add_blacklisted_tags', array(
				'script',
				'noscript',
				'style',
				'frame',
				'frameset',
				'object',
				'param',
				'applet',
				
				// Removed this form elements to make sure
				// Form works in AMP
				// 'form',
				// 'label',
				// 'input',
				// 'textarea',
				// 'select',
				// 'option',
				'link',
				'picture',

				// Sanitizers run after embed handlers, so if anything wasn't matched, it needs to be removed.
				'embed',
				'embedvideo',

				// Other weird ones
				'comments-count',

				// These are converted into amp-* versions
				//'img',
				//'video',
				//'audio',
				//'iframe',
			) );
		}
		private function get_blacklisted_attributes() {
			return $this->merge_defaults_with_args( 'add_blacklisted_attributes', array(
				'style',
				'size',
				'clear',
				'align',
				'valign',
			) );
		}
	}
}