Fix two exponential backtracking issues

See commonmark/commonmark.js@ce345929 and commonmark/commonmark.js#158
thephpleague · Mar 24, 2019 · 9248319 · 9248319
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -9,6 +9,10 @@ Updates should follow the [Keep a CHANGELOG](http://keepachangelog.com/) princip
  - Modified how URL normalization decodes certain characters in order to align with the JS library's output
  - Disallowed unescaped `(` in parenthesized link title
 
+### Fixed
+
+ - Fixed two exponential backtracking issues
+
 ## [0.18.3] - 2019-03-21
 
 This is a **security update** release.

diff --git a/src/Util/LinkParserHelper.php b/src/Util/LinkParserHelper.php
@@ -75,8 +75,8 @@ public static function parseLinkDestination(Cursor $cursor)
      */
     public static function parseLinkLabel(Cursor $cursor)
     {
-        $match = $cursor->match('/^\[(?:[^\\\\\[\]]|' . RegexHelper::PARTIAL_ESCAPED_CHAR . '|\\\\)*\]/');
-        if ($match === null || preg_match('/[^\\\\]\\\\\]$/', $match)) {
+        $match = $cursor->match('/^\[(?:[^\\\\\[\]]|\\\\.){0,1000}\]/');
+        if ($match === null) {
             return 0;
         }
 

diff --git a/src/Util/RegexHelper.php b/src/Util/RegexHelper.php
@@ -151,7 +151,7 @@ final class RegexHelper
     const REGEX_WHITESPACE = '/[ \t\n\x0b\x0c\x0d]+/';
     const REGEX_UNICODE_WHITESPACE_CHAR = '/^\pZ|\s/u';
     const REGEX_THEMATIC_BREAK = '/^(?:(?:\*[ \t]*){3,}|(?:_[ \t]*){3,}|(?:-[ \t]*){3,})[ \t]*$/';
-    const REGEX_LINK_DESTINATION_BRACES = '/^(?:' . '[<](?:[^ <>\\t\\n\\\\\\x00]' . '|' . self::PARTIAL_ESCAPED_CHAR . '|' . '\\\\)*[>]' . ')/';
+    const REGEX_LINK_DESTINATION_BRACES = '/^(?:<(?:[^ <>\\t\\n\\\\\\x00]|\\\\.)*>)/';
 
     /**
      * @deprecated Instance methods will be removed in 0.18 or 1.0 (whichever comes first)