Merge pull request #6965 from ampproject/feature/6059-img-to-amp-pixel

Replace `img` with `amp-pixel` when dealing with Facebook tracking pixel
ampproject · Mar 9, 2022 · b188731 · b188731
2 parents a93ddfe + e40d370
commit b188731
Show file tree

Hide file tree

Showing 2 changed files with 97 additions and 0 deletions.
diff --git a/includes/sanitizers/class-amp-img-sanitizer.php b/includes/sanitizers/class-amp-img-sanitizer.php
@@ -183,6 +183,26 @@ public function sanitize() {
 				continue;
 			}
 
+			// 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,
+					$attributes
+				);
+				$node->parentNode->replaceChild( $amp_pixel_node, $node );
+				continue;
+			}
+
 			// Short-circuit emoji images from needing to make requests out to https://s.w.org/.
 			if ( 'wp-smiley' === $node->getAttribute( Attribute::CLASS_ ) ) {
 				$node->setAttribute( Attribute::WIDTH, '72' );
@@ -552,4 +572,27 @@ private function is_gif_url( $url ) {
 		$path = wp_parse_url( $url, PHP_URL_PATH );
 		return substr( $path, -strlen( $ext ) ) === $ext;
 	}
+
+	/**
+	 * Determines if a URL is a known tracking pixel URL.
+	 *
+	 * Currently, only Facebook tracking pixel URL is detected.
+	 *
+	 * @since 2.2.2
+	 *
+	 * @param string $url URL to inspect.
+	 *
+	 * @return bool Returns true if $url is a tracking pixel URL.
+	 */
+	private static function is_tracking_pixel_url( $url ) {
+		$parsed_url = wp_parse_url( $url );
+
+		return (
+			isset( $parsed_url['host'], $parsed_url['path'] )
+			&&
+			'facebook.com' === str_replace( 'www.', '', $parsed_url['host'] )
+			&&
+			'/tr' === $parsed_url['path']
+		);
+	}
 }
diff --git a/tests/php/test-amp-img-sanitizer.php b/tests/php/test-amp-img-sanitizer.php
@@ -575,6 +575,16 @@ public function get_data() {
 					AMP_Tag_And_Attribute_Sanitizer::WRONG_PARENT_TAG,
 				],
 			],
+
+			'facebook_pixel_img_to_amp_pixel'          => [
+				'<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>',
+			],
 		];
 	}
 
@@ -923,4 +933,48 @@ public function test_process_picture_elements( $input, $args, $expected ) {
 
 		$this->assertEqualMarkup( $expected, $actual, "Actual content:\n$actual" );
 	}
+
+	/**
+	 * @return array
+	 */
+	public function get_data_for_test_is_tracking_pixel_url() {
+		return [
+			'facebook_pixel_url_no_ssl_no_www' => [
+				'url'      => 'http://facebook.com/tr?id=123456789012345',
+				'expected' => true,
+			],
+			'facebook_pixel_url_no_ssl_www'    => [
+				'url'      => 'http://www.facebook.com/tr?id=123456789012345',
+				'expected' => true,
+			],
+			'facebook_pixel_url_ssl_no_www'    => [
+				'url'      => 'https://facebook.com/tr?id=123456789012345',
+				'expected' => true,
+			],
+			'facebook_pixel_url_ssl_www'       => [
+				'url'      => 'https://www.facebook.com/tr?id=123456789012345',
+				'expected' => true,
+			],
+			'facebook_page_url'                => [
+				'url'      => 'https://www.facebook.com/traffic?id=123456789012345',
+				'expected' => false,
+			],
+			'relative_url'                     => [
+				'url'      => '/tr?id=123456789012345',
+				'expected' => false,
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider get_data_for_test_is_tracking_pixel_url()
+	 *
+	 * @covers ::is_tracking_pixel_url()
+	 */
+	public function test_is_tracking_pixel_url( $url, $expected ) {
+		$this->assertEquals(
+			$expected,
+			$this->call_private_static_method( AMP_Img_Sanitizer::class, 'is_tracking_pixel_url', [ $url ] )
+		);
+	}
 }