From dd9722fac06e16d12f0780883c52d6b8651f3717 Mon Sep 17 00:00:00 2001
From: John Blackbourn <johnbillion@git.wordpress.org>
Date: Sat, 5 Sep 2015 21:28:50 +0000
Subject: [PATCH] Bail out early from `esc_url()` if the URL becomes empty
 after stripping out disallowed characters.

Fixes #28015
Props jesin for the unit test


git-svn-id: https://develop.svn.wordpress.org/trunk@33923 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/formatting.php            | 5 +++++
 tests/phpunit/tests/formatting/EscUrl.php | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index 29f67fedb9..be8ea6c994 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -3277,6 +3277,11 @@ function esc_url( $url, $protocols = null, $_context = 'display' ) {
 
 	$url = str_replace( ' ', '%20', $url );
 	$url = preg_replace('|[^a-z0-9-~+_.?#=!&;,/:%@$\|*\'()\\x80-\\xff]|i', '', $url);
+
+	if ( '' === $url ) {
+		return $url;
+	}
+
 	if ( 0 !== stripos( $url, 'mailto:' ) ) {
 		$strip = array('%0d', '%0a', '%0D', '%0A');
 		$url = _deep_replace($strip, $url);
diff --git a/tests/phpunit/tests/formatting/EscUrl.php b/tests/phpunit/tests/formatting/EscUrl.php
index c61522d287..1289fd7c76 100644
--- a/tests/phpunit/tests/formatting/EscUrl.php
+++ b/tests/phpunit/tests/formatting/EscUrl.php
@@ -171,5 +171,11 @@ EOT;
 		$this->assertEquals( 'mailto:?body=Hi%20there,%20I%20thought%20you%20might%20want%20to%20sign%20up%20for%20this%20newsletter', $email_link );
 	}
 
+	/**
+	 * @ticket 28015
+	 */
+	function test_invalid_charaters() {
+		$this->assertEmpty( esc_url_raw('"^[]<>{}`') );
+	}
 
 }