From 654c413990e5750b49ba5cff1ab99e332b7177e4 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Mon, 21 Oct 2019 20:41:04 +0000
Subject: [PATCH] Comments: Add `rel="nofollow ugc"` attribute when converting
 plain URLs to `<a>` tags in comments via `make_clickable()`.

Introduce `make_clickable_rel` filter for the `rel` value that is added to URL matches converted to links.

This is a follow-up to [46349], which added the `rel="nofollow ugc"` attribute to existing `<a>` tags in comments via `wp_rel_ugc()`.

UGC stands for User Generated Content, and the `ugc` attribute value is recommended for links within user generated content, such as comments and forum posts.

See https://webmasters.googleblog.com/2019/09/evolving-nofollow-new-ways-to-identify.html.

Props blogginglife, SergeyBiryukov.
Reviewed by desrosj, audrasjb.
Fixes #48022.
Built from https://develop.svn.wordpress.org/trunk@46564


git-svn-id: http://core.svn.wordpress.org/trunk@46361 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/formatting.php | 33 ++++++++++++++++++++++++++++++---
 wp-includes/version.php    |  2 +-
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index a5eddae784..1c94f2906e 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -2835,7 +2835,24 @@ function _make_url_clickable_cb( $matches ) {
 		return $matches[0];
 	}
 
-	return $matches[1] . "<a href=\"$url\" rel=\"nofollow\">$url</a>" . $suffix;
+	if ( 'comment_text' === current_filter() ) {
+		$rel = 'nofollow ugc';
+	} else {
+		$rel = 'nofollow';
+	}
+
+	/**
+	 * Filters the rel value that is added to URL matches converted to links.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param string $rel The rel value.
+	 * @param string $url The matched URL being converted to a link tag.
+	 */
+	$rel = apply_filters( 'make_clickable_rel', $rel, $url );
+	$rel = esc_attr( $rel );
+
+	return $matches[1] . "<a href=\"$url\" rel=\"$rel\">$url</a>" . $suffix;
 }
 
 /**
@@ -2865,7 +2882,17 @@ function _make_web_ftp_clickable_cb( $matches ) {
 		return $matches[0];
 	}
 
-	return $matches[1] . "<a href=\"$dest\" rel=\"nofollow\">$dest</a>$ret";
+	if ( 'comment_text' === current_filter() ) {
+		$rel = 'nofollow ugc';
+	} else {
+		$rel = 'nofollow';
+	}
+
+	/** This filter is documented in wp-includes/formatting.php */
+	$rel = apply_filters( 'make_clickable_rel', $rel, $dest );
+	$rel = esc_attr( $rel );
+
+	return $matches[1] . "<a href=\"$dest\" rel=\"$rel\">$dest</a>$ret";
 }
 
 /**
@@ -3148,7 +3175,7 @@ function wp_targeted_link_rel_callback( $matches ) {
 	 *
 	 * @since 5.1.0
 	 *
-	 * @param string The rel values.
+	 * @param string $rel       The rel values.
 	 * @param string $link_html The matched content of the link tag including all HTML attributes.
 	 */
 	$rel = apply_filters( 'wp_targeted_link_rel', 'noopener noreferrer', $link_html );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 28ff42bcd6..786e6f82e8 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-RC1-46563';
+$wp_version = '5.3-RC1-46564';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.