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<title>[46896] trunk: Prevent stored XSS in the block editor.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/46896">46896</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/46896","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>whyisjake</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2019-12-12 18:00:45 +0000 (Thu, 12 Dec 2019)</dd>
</dl>
<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Prevent stored XSS in the block editor.
Prevent escaped unicode characters become unescaped in unsafe HTML during JSON decoding.
Props: aduth, epiqueras, </pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludesblocksphp">trunk/src/wp-includes/blocks.php</a></li>
<li><a href="#trunksrcwpincludesdefaultfiltersphp">trunk/src/wp-includes/default-filters.php</a></li>
<li><a href="#trunksrcwpincludesformattingphp">trunk/src/wp-includes/formatting.php</a></li>
<li><a href="#trunktestsphpunittestsblocksblocktypephp">trunk/tests/phpunit/tests/blocks/block-type.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludesblocksphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/blocks.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/blocks.php 2019-12-12 17:52:18 UTC (rev 46895)
+++ trunk/src/wp-includes/blocks.php 2019-12-12 18:00:45 UTC (rev 46896)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -74,11 +74,11 @@
</span><span class="cx" style="display: block; padding: 0 10px"> * @since 5.0.0
</span><span class="cx" style="display: block; padding: 0 10px"> * @see parse_blocks()
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- * @param string $block_type Full Block type to look for.
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * @param string $block_name Full Block type to look for.
</ins><span class="cx" style="display: block; padding: 0 10px"> * @param int|string|WP_Post|null $post Optional. Post content, post ID, or post object. Defaults to global $post.
</span><span class="cx" style="display: block; padding: 0 10px"> * @return bool Whether the post content contains the specified block.
</span><span class="cx" style="display: block; padding: 0 10px"> */
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-function has_block( $block_type, $post = null ) {
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+function has_block( $block_name, $post = null ) {
</ins><span class="cx" style="display: block; padding: 0 10px"> if ( ! has_blocks( $post ) ) {
</span><span class="cx" style="display: block; padding: 0 10px"> return false;
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -90,7 +90,30 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- return false !== strpos( $post, '<!-- wp:' . $block_type . ' ' );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ /*
+ * Normalize block name to include namespace, if provided as non-namespaced.
+ * This matches behavior for WordPress 5.0.0 - 5.3.0 in matching blocks by
+ * their serialized names.
+ */
+ if ( false === strpos( $block_name, '/' ) ) {
+ $block_name = 'core/' . $block_name;
+ }
+
+ // Test for existence of block by its fully qualified name.
+ $has_block = false !== strpos( $post, '<!-- wp:' . $block_name . ' ' );
+
+ if ( ! $has_block ) {
+ /*
+ * If the given block name would serialize to a different name, test for
+ * existence by the serialized form.
+ */
+ $serialized_block_name = strip_core_block_namespace( $block_name );
+ if ( $serialized_block_name !== $block_name ) {
+ $has_block = false !== strpos( $post, '<!-- wp:' . $serialized_block_name . ' ' );
+ }
+ }
+
+ return $has_block;
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -114,6 +137,207 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * Given an array of attributes, returns a string in the serialized attributes
+ * format prepared for post content.
+ *
+ * The serialized result is a JSON-encoded string, with unicode escape sequence
+ * substitution for characters which might otherwise interfere with embedding
+ * the result in an HTML comment.
+ *
+ * @since 5.3.1
+ *
+ * @param array $attributes Attributes object.
+ * @return string Serialized attributes.
+ */
+function serialize_block_attributes( $block_attributes ) {
+ $encoded_attributes = json_encode( $block_attributes );
+ $encoded_attributes = preg_replace( '/--/', '\\u002d\\u002d', $encoded_attributes );
+ $encoded_attributes = preg_replace( '/</', '\\u003c', $encoded_attributes );
+ $encoded_attributes = preg_replace( '/>/', '\\u003e', $encoded_attributes );
+ $encoded_attributes = preg_replace( '/&/', '\\u0026', $encoded_attributes );
+ // Regex: /\\"/
+ $encoded_attributes = preg_replace( '/\\\\"/', '\\u0022', $encoded_attributes );
+
+ return $encoded_attributes;
+}
+
+/**
+ * Returns the block name to use for serialization. This will remove the default
+ * "core/" namespace from a block name.
+ *
+ * @since 5.3.1
+ *
+ * @param string $block_name Original block name.
+ * @return string Block name to use for serialization.
+ */
+function strip_core_block_namespace( $block_name = null ) {
+ if ( is_string( $block_name ) && 0 === strpos( $block_name, 'core/' ) ) {
+ return substr( $block_name, 5 );
+ }
+
+ return $block_name;
+}
+
+/**
+ * Returns the content of a block, including comment delimiters.
+ *
+ * @since 5.3.1
+ *
+ * @param string $block_name Block name.
+ * @param array $attributes Block attributes.
+ * @param string $content Block save content.
+ * @return string Comment-delimited block content.
+ */
+function get_comment_delimited_block_content( $block_name = null, $block_attributes, $block_content ) {
+ if ( is_null( $block_name ) ) {
+ return $block_content;
+ }
+
+ $serialized_block_name = strip_core_block_namespace( $block_name );
+ $serialized_attributes = empty( $block_attributes ) ? '' : serialize_block_attributes( $block_attributes ) . ' ';
+
+ if ( empty( $block_content ) ) {
+ return sprintf( '<!-- wp:%s %s/-->', $serialized_block_name, $serialized_attributes );
+ }
+
+ return sprintf(
+ '<!-- wp:%s %s-->%s<!-- /wp:%s -->',
+ $serialized_block_name,
+ $serialized_attributes,
+ $block_content,
+ $serialized_block_name
+ );
+}
+
+/**
+ * Returns the content of a block, including comment delimiters, serializing all
+ * attributes from the given parsed block.
+ *
+ * This should be used when preparing a block to be saved to post content.
+ * Prefer `render_block` when preparing a block for display. Unlike
+ * `render_block`, this does not evaluate a block's `render_callback`, and will
+ * instead preserve the markup as parsed.
+ *
+ * @since 5.3.1
+ *
+ * @param WP_Block_Parser_Block $block A single parsed block object.
+ * @return string String of rendered HTML.
+ */
+function serialize_block( $block ) {
+ $block_content = '';
+
+ $index = 0;
+ foreach ( $block['innerContent'] as $chunk ) {
+ $block_content .= is_string( $chunk ) ? $chunk : serialize_block( $block['innerBlocks'][ $index++ ] );
+ }
+
+ if ( ! is_array( $block['attrs'] ) ) {
+ $block['attrs'] = array();
+ }
+
+ return get_comment_delimited_block_content(
+ $block['blockName'],
+ $block['attrs'],
+ $block_content
+ );
+}
+
+/**
+ * Returns a joined string of the aggregate serialization of the given parsed
+ * blocks.
+ *
+ * @since 5.3.1
+ *
+ * @param WP_Block_Parser_Block[] $blocks Parsed block objects.
+ * @return string String of rendered HTML.
+ */
+function serialize_blocks( $blocks ) {
+ return implode( '', array_map( 'serialize_block', $blocks ) );
+}
+
+/**
+ * Filters and sanitizes block content to remove non-allowable HTML from
+ * parsed block attribute values.
+ *
+ * @since 5.3.1
+ *
+ * @param string $text Text that may contain block content.
+ * @param array[]|string $allowed_html An array of allowed HTML elements
+ * and attributes, or a context name
+ * such as 'post'.
+ * @param string[] $allowed_protocols Array of allowed URL protocols.
+ * @return string The filtered and sanitized content result.
+ */
+function filter_block_content( $text, $allowed_html = 'post', $allowed_protocols = array() ) {
+ $result = '';
+
+ $blocks = parse_blocks( $text );
+ foreach ( $blocks as $block ) {
+ $block = filter_block_kses( $block, $allowed_html, $allowed_protocols );
+ $result .= serialize_block( $block );
+ }
+
+ return $result;
+}
+
+/**
+ * Filters and sanitizes a parsed block to remove non-allowable HTML from block
+ * attribute values.
+ *
+ * @since 5.3.1
+ *
+ * @param WP_Block_Parser_Block $block The parsed block object.
+ * @param array[]|string $allowed_html An array of allowed HTML
+ * elements and attributes, or a
+ * context name such as 'post'.
+ * @param string[] $allowed_protocols Allowed URL protocols.
+ * @return array The filtered and sanitized block object result.
+ */
+function filter_block_kses( $block, $allowed_html, $allowed_protocols = array() ) {
+ $block['attrs'] = filter_block_kses_value( $block['attrs'], $allowed_html, $allowed_protocols );
+
+ if ( is_array( $block['innerBlocks'] ) ) {
+ foreach ( $block['innerBlocks'] as $i => $inner_block ) {
+ $block['innerBlocks'][ $i ] = filter_block_kses( $inner_block, $allowed_html, $allowed_protocols );
+ }
+ }
+
+ return $block;
+}
+
+/**
+ * Filters and sanitizes a parsed block attribute value to remove non-allowable
+ * HTML.
+ *
+ * @since 5.3.1
+ *
+ * @param mixed $value The attribute value to filter.
+ * @param array[]|string $allowed_html An array of allowed HTML elements
+ * and attributes, or a context name
+ * such as 'post'.
+ * @param string[] $allowed_protocols Array of allowed URL protocols.
+ * @return array The filtered and sanitized result.
+ */
+function filter_block_kses_value( $value, $allowed_html, $allowed_protocols = array() ) {
+ if ( is_array( $value ) ) {
+ foreach ( $value as $key => $inner_value ) {
+ $filtered_key = filter_block_kses_value( $key, $allowed_html, $allowed_protocols );
+ $filtered_value = filter_block_kses_value( $inner_value, $allowed_html, $allowed_protocols );
+
+ if ( $filtered_key !== $key ) {
+ unset( $value[ $key ] );
+ }
+
+ $value[ $filtered_key ] = $filtered_value;
+ }
+ } elseif ( is_string( $value ) ) {
+ return wp_kses( $value, $allowed_html, $allowed_protocols );
+ }
+
+ return $value;
+}
+
+/**
</ins><span class="cx" style="display: block; padding: 0 10px"> * Parses blocks out of a content string, and renders those appropriate for the excerpt.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span><span class="cx" style="display: block; padding: 0 10px"> * As the excerpt should be a small string of text relevant to the full post content,
</span></span></pre></div>
<a id="trunksrcwpincludesdefaultfiltersphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/default-filters.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/default-filters.php 2019-12-12 17:52:18 UTC (rev 46895)
+++ trunk/src/wp-includes/default-filters.php 2019-12-12 18:00:45 UTC (rev 46896)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -243,6 +243,7 @@
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'tiny_mce_before_init', '_mce_set_direction' );
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'teeny_mce_before_init', '_mce_set_direction' );
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'pre_kses', 'wp_pre_kses_less_than' );
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+add_filter( 'pre_kses', 'wp_pre_kses_block_attributes', 10, 3 );
</ins><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'sanitize_title', 'sanitize_title_with_dashes', 10, 3 );
</span><span class="cx" style="display: block; padding: 0 10px"> add_action( 'check_comment_flood', 'check_comment_flood_db', 10, 4 );
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'comment_flood_filter', 'wp_throttle_comment_flood', 10, 3 );
</span></span></pre></div>
<a id="trunksrcwpincludesformattingphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/formatting.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/formatting.php 2019-12-12 17:52:18 UTC (rev 46895)
+++ trunk/src/wp-includes/formatting.php 2019-12-12 18:00:45 UTC (rev 46896)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -4905,6 +4905,31 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * Remove non-allowable HTML from parsed block attribute values when filtering
+ * in the post context.
+ *
+ * @since 5.3.1
+ *
+ * @param string $string Content to be run through KSES.
+ * @param array[]|string $allowed_html An array of allowed HTML elements
+ * and attributes, or a context name
+ * such as 'post'.
+ * @param string[] $allowed_protocols Array of allowed URL protocols.
+ * @return string Filtered text to run through KSES.
+ */
+function wp_pre_kses_block_attributes( $string, $allowed_html, $allowed_protocols ) {
+ /*
+ * `filter_block_content` is expected to call `wp_kses`. Temporarily remove
+ * the filter to avoid recursion.
+ */
+ remove_filter( 'pre_kses', 'wp_pre_kses_block_attributes', 10 );
+ $string = filter_block_content( $string, $allowed_html, $allowed_protocols );
+ add_filter( 'pre_kses', 'wp_pre_kses_block_attributes', 10, 3 );
+
+ return $string;
+}
+
+/**
</ins><span class="cx" style="display: block; padding: 0 10px"> * WordPress implementation of PHP sprintf() with filters.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span><span class="cx" style="display: block; padding: 0 10px"> * @since 2.5.0
</span></span></pre></div>
<a id="trunktestsphpunittestsblocksblocktypephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/blocks/block-type.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/blocks/block-type.php 2019-12-12 17:52:18 UTC (rev 46895)
+++ trunk/tests/phpunit/tests/blocks/block-type.php 2019-12-12 18:00:45 UTC (rev 46896)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -304,6 +304,24 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $this->assertFalse( has_block( 'core/fake' ) );
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ public function test_post_has_block_serialized_name() {
+ $content = '<!-- wp:serialized /--><!-- wp:core/normalized /--><!-- wp:plugin/third-party /-->';
+
+ $this->assertTrue( has_block( 'core/serialized', $content ) );
+
+ /*
+ * Technically, `has_block` should receive a "full" (normalized, parsed)
+ * block name. But this test conforms to expected pre-5.3.1 behavior.
+ */
+ $this->assertTrue( has_block( 'serialized', $content ) );
+ $this->assertTrue( has_block( 'core/normalized', $content ) );
+ $this->assertTrue( has_block( 'normalized', $content ) );
+ $this->assertFalse( has_block( 'plugin/normalized', $content ) );
+ $this->assertFalse( has_block( 'plugin/serialized', $content ) );
+ $this->assertFalse( has_block( 'third-party', $content ) );
+ $this->assertFalse( has_block( 'core/third-party', $content ) );
+ }
+
</ins><span class="cx" style="display: block; padding: 0 10px"> /**
</span><span class="cx" style="display: block; padding: 0 10px"> * Renders a test block without content.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span></span></pre>
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