From 7206b554d91856723f7836d062cb416de5e48063 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Tue, 12 Mar 2019 22:15:37 +0000
Subject: [PATCH] Formatting: Improve `rel="nofollow"` handling in comments.

Merges [44833] to the 5.1 branch.

git-svn-id: https://develop.svn.wordpress.org/branches/5.1@44834 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/formatting.php | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index b5c4982141..6b44820dad 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -3004,10 +3004,12 @@ function wp_rel_nofollow_callback( $matches ) {
 	$atts = shortcode_parse_atts( $matches[1] );
 	$rel  = 'nofollow';
 
-	if ( preg_match( '%href=["\'](' . preg_quote( set_url_scheme( home_url(), 'http' ) ) . ')%i', $text ) ||
-		preg_match( '%href=["\'](' . preg_quote( set_url_scheme( home_url(), 'https' ) ) . ')%i', $text ) ) {
-
-		return "<a $text>";
+	if ( ! empty( $atts['href'] ) ) {
+		if ( in_array( strtolower( wp_parse_url( $atts['href'], PHP_URL_SCHEME ) ), array( 'http', 'https' ), true ) ) {
+			if ( strtolower( wp_parse_url( $atts['href'], PHP_URL_HOST ) ) === strtolower( wp_parse_url( home_url(), PHP_URL_HOST ) ) ) {
+				return "<a $text>";
+			}
+		}
 	}
 
 	if ( ! empty( $atts['rel'] ) ) {
@@ -3020,11 +3022,11 @@ function wp_rel_nofollow_callback( $matches ) {
 
 		$html = '';
 		foreach ( $atts as $name => $value ) {
-			$html .= "{$name}=\"$value\" ";
+			$html .= "{$name}=\"" . esc_attr( $value ) . "\" ";
 		}
 		$text = trim( $html );
 	}
-	return "<a $text rel=\"$rel\">";
+	return "<a $text rel=\"" . esc_attr( $rel ) . "\">";
 }
 
 /**