Media: Use Document-Isolation-Policy for cross-origin isolation

src/wp-includes/media.php

@@ -6393,6 +6393,12 @@ function wp_set_client_side_media_processing_flag(): void {
 
 	wp_add_inline_script( 'wp-block-editor', 'window.__clientSideMediaProcessing = true', 'before' );
 
+	$chromium_version = wp_get_chromium_major_version();
+
+	if ( null !== $chromium_version && $chromium_version >= 137 ) {
+		wp_add_inline_script( 'wp-block-editor', 'window.__documentIsolationPolicy = true;', 'before' );
+	}
+
 	/*
 	 * Register the @wordpress/vips/worker script module as a dynamic dependency
 	 * of the wp-upload-media classic script. This ensures it is included in the
@@ -6405,15 +6411,33 @@ function wp_set_client_side_media_processing_flag(): void {
 	);
 }
 
+/**
+ * Returns the major Chrome/Chromium version from the current request's User-Agent.
+ *
+ * Matches all Chromium-based browsers (Chrome, Edge, Opera, Brave).
+ *
+ * @since 7.0.0
+ *
+ * @return int|null The major Chrome version, or null if not a Chromium browser.
+ */
+function wp_get_chromium_major_version(): ?int {
+	if ( empty( $_SERVER['HTTP_USER_AGENT'] ) ) {
+		return null;
+	}
+	if ( preg_match( '#Chrome/(\d+)#', $_SERVER['HTTP_USER_AGENT'], $matches ) ) {
+		return (int) $matches[1];
+	}
+	return null;
+}
+
 /**
  * Enables cross-origin isolation in the block editor.
  *
  * Required for enabling SharedArrayBuffer for WebAssembly-based
- * media processing in the editor.
+ * media processing in the editor. Uses Document-Isolation-Policy
+ * on supported browsers (Chromium 137+).
  *
  * @since 7.0.0
- *
- * @link https://web.dev/coop-coep/
  */
 function wp_set_up_cross_origin_isolation(): void {
 	if ( ! wp_is_client_side_media_processing_enabled() ) {
@@ -6439,26 +6463,22 @@ function wp_set_up_cross_origin_isolation(): void {
 }
 
 /**
- * Starts an output buffer to send cross-origin isolation headers.
+ * Sends the Document-Isolation-Policy header for cross-origin isolation.
  *
- * Sends headers and uses an output buffer to add crossorigin="anonymous"
- * attributes where needed.
+ * Uses an output buffer to add crossorigin="anonymous" where needed.
  *
  * @since 7.0.0
- *
- * @link https://web.dev/coop-coep/
- *
- * @global bool $is_safari
  */
 function wp_start_cross_origin_isolation_output_buffer(): void {
-	global $is_safari;
+	$chromium_version = wp_get_chromium_major_version();
 
-	$coep = $is_safari ? 'require-corp' : 'credentialless';
+	if ( null === $chromium_version || $chromium_version < 137 ) {
+		return;
+	}
 
 	ob_start(
-		static function ( string $output ) use ( $coep ): string {
-			header( 'Cross-Origin-Opener-Policy: same-origin' );
-			header( "Cross-Origin-Embedder-Policy: $coep" );
+		static function ( string $output ): string {
+			header( 'Document-Isolation-Policy: isolate-and-credentialless' );
 
 			return wp_add_crossorigin_attributes( $output );
 		}

tests/phpunit/tests/media/wpCrossOriginIsolation.php

@@ -0,0 +1,152 @@
+<?php
+
+/**
+ * Tests for cross-origin isolation functions.
+ *
+ * @group media
+ * @covers ::wp_set_up_cross_origin_isolation
+ * @covers ::wp_start_cross_origin_isolation_output_buffer
+ */
+class Tests_Media_wpCrossOriginIsolation extends WP_UnitTestCase {
+
+	/**
+	 * Original HTTP_USER_AGENT value.
+	 *
+	 * @var string|null
+	 */
+	private $original_user_agent;
+
+	public function set_up() {
+		parent::set_up();
+		$this->original_user_agent = isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : null;
+	}
+
+	public function tear_down() {
+		if ( null === $this->original_user_agent ) {
+			unset( $_SERVER['HTTP_USER_AGENT'] );
+		} else {
+			$_SERVER['HTTP_USER_AGENT'] = $this->original_user_agent;
+		}
+
+		// Clean up any output buffers started during tests.
+		while ( ob_get_level() > 1 ) {
+			ob_end_clean();
+		}
+
+		remove_all_filters( 'wp_client_side_media_processing_enabled' );
+		parent::tear_down();
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_returns_early_when_client_side_processing_disabled() {
+		add_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
+
+		// Should not error or start an output buffer.
+		$level_before = ob_get_level();
+		wp_set_up_cross_origin_isolation();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before, $level_after );
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_returns_early_when_no_screen() {
+		// No screen is set, so it should return early.
+		$level_before = ob_get_level();
+		wp_set_up_cross_origin_isolation();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before, $level_after );
+	}
+
+	/**
+	 * This test must run in a separate process because the output buffer
+	 * callback sends HTTP headers via header(), which would fail in the
+	 * main PHPUnit process where output has already started.
+	 *
+	 * @ticket 64766
+	 *
+	 * @runInSeparateProcess
+	 * @preserveGlobalState disabled
+	 */
+	public function test_starts_output_buffer_for_chrome_137() {
+		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36';
+
+		$level_before = ob_get_level();
+		wp_start_cross_origin_isolation_output_buffer();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before + 1, $level_after, 'Output buffer should be started for Chrome 137.' );
+
+		ob_end_clean();
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_does_not_start_output_buffer_for_chrome_136() {
+		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36';
+
+		$level_before = ob_get_level();
+		wp_start_cross_origin_isolation_output_buffer();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before, $level_after, 'Output buffer should not be started for Chrome < 137.' );
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_does_not_start_output_buffer_for_firefox() {
+		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; rv:128.0) Gecko/20100101 Firefox/128.0';
+
+		$level_before = ob_get_level();
+		wp_start_cross_origin_isolation_output_buffer();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before, $level_after, 'Output buffer should not be started for Firefox.' );
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_does_not_start_output_buffer_for_safari() {
+		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.5 Safari/605.1.15';
+
+		$level_before = ob_get_level();
+		wp_start_cross_origin_isolation_output_buffer();
+		$level_after = ob_get_level();
+
+		$this->assertSame( $level_before, $level_after, 'Output buffer should not be started for Safari.' );
+	}
+
+	/**
+	 * This test must run in a separate process because the output buffer
+	 * callback sends HTTP headers via header(), which would fail in the
+	 * main PHPUnit process where output has already started.
+	 *
+	 * @ticket 64766
+	 *
+	 * @runInSeparateProcess
+	 * @preserveGlobalState disabled
+	 */
+	public function test_output_buffer_adds_crossorigin_attributes() {
+		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36';
+
+		// Start an outer buffer to capture the callback-processed output.
+		ob_start();
+
+		wp_start_cross_origin_isolation_output_buffer();
+		echo '<img src="https://external.example.com/image.jpg" />';
+
+		// Flush the inner buffer to trigger the callback, sending processed output to the outer buffer.
+		ob_end_flush();
+		$output = ob_get_clean();
+
+		$this->assertStringContainsString( 'crossorigin="anonymous"', $output );
+	}
+}

tests/phpunit/tests/media/wpGetChromiumMajorVersion.php

@@ -0,0 +1,69 @@
+<?php
+
+/**
+ * Tests for the `wp_get_chromium_major_version()` function.
+ *
+ * @group media
+ * @covers ::wp_get_chromium_major_version
+ */
+class Tests_Media_wpGetChromiumMajorVersion extends WP_UnitTestCase {
+
+	/**
+	 * Original HTTP_USER_AGENT value.
+	 *
+	 * @var string|null
+	 */
+	private $original_user_agent;
+
+	public function set_up() {
+		parent::set_up();
+		$this->original_user_agent = isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : null;
+	}
+
+	public function tear_down() {
+		if ( null === $this->original_user_agent ) {
+			unset( $_SERVER['HTTP_USER_AGENT'] );
+		} else {
+			$_SERVER['HTTP_USER_AGENT'] = $this->original_user_agent;
+		}
+		parent::tear_down();
+	}
+
+	/**
+	 * @ticket 64766
+	 */
+	public function test_returns_null_when_no_user_agent() {
+		unset( $_SERVER['HTTP_USER_AGENT'] );
+		$this->assertNull( wp_get_chromium_major_version() );
+	}
+
+	/**
+	 * @ticket 64766
+	 *
+	 * @dataProvider data_user_agents
+	 *
+	 * @param string   $user_agent The user agent string.
+	 * @param int|null $expected   The expected Chromium major version, or null.
+	 */
+	public function test_returns_expected_version( $user_agent, $expected ) {
+		$_SERVER['HTTP_USER_AGENT'] = $user_agent;
+		$this->assertSame( $expected, wp_get_chromium_major_version() );
+	}
+
+	/**
+	 * Data provider for test_returns_expected_version.
+	 *
+	 * @return array[]
+	 */
+	public function data_user_agents() {
+		return array(
+			'empty user agent'   => array( '', null ),
+			'Firefox'            => array( 'Mozilla/5.0 (Windows NT 10.0; rv:128.0) Gecko/20100101 Firefox/128.0', null ),
+			'Safari'             => array( 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.5 Safari/605.1.15', null ),
+			'Chrome 137'         => array( 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36', 137 ),
+			'Edge 137'           => array( 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36 Edg/137.0.0.0', 137 ),
+			'Opera (Chrome 136)' => array( 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36 OPR/122.0.0.0', 136 ),
+			'Chrome 100'         => array( 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.75 Safari/537.36', 100 ),
+		);
+	}
+}