From e40d370cd03e06b0f86835a92822c21b979930d1 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Wed, 9 Mar 2022 09:25:53 -0800
Subject: [PATCH] Copy referrerpolicy attribute from img to amp-pixel

---
 includes/sanitizers/class-amp-img-sanitizer.php | 14 ++++++++++----
 tests/php/test-amp-img-sanitizer.php            |  5 +++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/includes/sanitizers/class-amp-img-sanitizer.php b/includes/sanitizers/class-amp-img-sanitizer.php
index bbf0ab12fb3..9188ac2f05e 100644
--- a/includes/sanitizers/class-amp-img-sanitizer.php
+++ b/includes/sanitizers/class-amp-img-sanitizer.php
@@ -185,13 +185,19 @@ public function sanitize() {
 
 			// Replace img with amp-pixel when dealing with tracking pixels.
 			if ( self::is_tracking_pixel_url( $node->getAttribute( Attribute::SRC ) ) ) {
+				$attributes = [
+					Attribute::SRC    => $node->getAttribute( Attribute::SRC ),
+					Attribute::LAYOUT => Layout::NODISPLAY,
+				];
+				foreach ( [ Attribute::REFERRERPOLICY ] as $allowed_attribute ) {
+					if ( $node->hasAttribute( $allowed_attribute ) ) {
+						$attributes[ $allowed_attribute ] = $node->getAttribute( $allowed_attribute );
+					}
+				}
 				$amp_pixel_node = AMP_DOM_Utils::create_node(
 					$this->dom,
 					Extension::PIXEL,
-					[
-						Attribute::SRC    => $node->getAttribute( Attribute::SRC ),
-						Attribute::LAYOUT => Layout::NODISPLAY,
-					]
+					$attributes
 				);
 				$node->parentNode->replaceChild( $amp_pixel_node, $node );
 				continue;
diff --git a/tests/php/test-amp-img-sanitizer.php b/tests/php/test-amp-img-sanitizer.php
index f10d5a4f3e9..9742e32fbfb 100644
--- a/tests/php/test-amp-img-sanitizer.php
+++ b/tests/php/test-amp-img-sanitizer.php
@@ -580,6 +580,11 @@ public function get_data() {
 				'<img height="1" width="1" style="display:none" alt="fbpx" src="https://www.facebook.com/tr?id=123456789012345&ev=PageView&noscript=1" />',
 				'<amp-pixel src="https://www.facebook.com/tr?id=123456789012345&amp;ev=PageView&amp;noscript=1" layout="nodisplay"></amp-pixel>',
 			],
+
+			'facebook_pixel_img_to_amp_pixel_with_referrer' => [
+				'<img height="1" width="1" style="display:none" alt="fbpx" src="https://facebook.com/tr?id=123456789012345&ev=PageView&noscript=1" referrerpolicy="no-referrer">',
+				'<amp-pixel src="https://facebook.com/tr?id=123456789012345&amp;ev=PageView&amp;noscript=1" layout="nodisplay" referrerpolicy="no-referrer"></amp-pixel>',
+			],
 		];
 	}