From 726d4ef44a676de2e2af0c3b1861c9429a257196 Mon Sep 17 00:00:00 2001
From: Aidan Woods <aidantwoods@gmail.com>
Date: Mon, 9 Apr 2018 02:32:23 +0100
Subject: [PATCH] Sanity checks before starting regex engine

---
 Parsedown.php | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Parsedown.php b/Parsedown.php
index 6b7ff86..7fa06e3 100644
--- a/Parsedown.php
+++ b/Parsedown.php
@@ -829,8 +829,9 @@ class Parsedown
 
     protected function blockReference($Line)
     {
-        if (preg_match('/^\[(.+?)\]:[ ]*+<?(\S+?)>?(?:[ ]+["\'(](.+)["\')])?[ ]*+$/', $Line['text'], $matches))
-        {
+        if (strpos($Line['text'], ']') !== false
+            and preg_match('/^\[(.+?)\]:[ ]*+<?(\S+?)>?(?:[ ]+["\'(](.+)["\')])?[ ]*+$/', $Line['text'], $matches)
+        ) {
             $id = strtolower($matches[1]);
 
             $Data = array(
@@ -1448,8 +1449,9 @@ class Parsedown
 
     protected function inlineSpecialCharacter($Excerpt)
     {
-        if (preg_match('/^&(#?+[0-9a-zA-Z]++);/', $Excerpt['text'], $matches))
-        {
+        if ($Excerpt['text'][1] !== ' ' and strpos($Excerpt['text'], ';') !== false
+            and preg_match('/^&(#?+[0-9a-zA-Z]++);/', $Excerpt['text'], $matches)
+        ) {
             return array(
                 'element' => array('rawHtml' => "&{$matches[1]};"),
                 'extent' => strlen($matches[0]),
@@ -1489,8 +1491,9 @@ class Parsedown
             return;
         }
 
-        if (preg_match('/\bhttps?+:[\/]{2}[^\s<]+\b\/*+/ui', $Excerpt['context'], $matches, PREG_OFFSET_CAPTURE))
-        {
+        if (strpos($Excerpt['context'], 'http') !== false
+            and preg_match('/\bhttps?+:[\/]{2}[^\s<]+\b\/*+/ui', $Excerpt['context'], $matches, PREG_OFFSET_CAPTURE)
+        ) {
             $url = $matches[0][0];
 
             $Inline = array(