diff --git a/README.md b/README.md
index f142dcb..04f0fb4 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,12 @@ The ExpressionEngine Discussion Forum Module allows you to create and manage a f
 
 ## Changelog
 
+### 5.1.3
+
+- Fixed PHP deprecation issues.
+- Fixed bug where Superadmin were not given full permissions in rare cases.
+- Fixed Invalid reference to PATH_ADDONS ([#5](https://github.com/ExpressionEngine/Forum/issues/5))
+
 ### 5.1.2
 
 - Fixed PHP deprecation issues.
diff --git a/system/user/addons/forum/Model/Post.php b/system/user/addons/forum/Model/Post.php
index 48c602d..a6fcf09 100644
--- a/system/user/addons/forum/Model/Post.php
+++ b/system/user/addons/forum/Model/Post.php
@@ -131,8 +131,13 @@ public static function onBeforeBulkDelete($delete_ids)
 
     public static function onAfterBulkDelete()
     {
-        require_once PATH_ADDONS . 'forum/mod.forum.php';
-        require_once PATH_ADDONS . 'forum/mod.forum_core.php';
+        foreach(['forum/mod.forum.php', 'forum/mod.forum_core.php'] as $file) {
+            if (file_exists(PATH_THIRD . $file)) {
+                require_once PATH_THIRD . $file;
+            } else {
+                require_once PATH_ADDONS . $file;
+            }
+        }
 
         $forum_core = new \Forum_Core();
 
diff --git a/system/user/addons/forum/Model/Topic.php b/system/user/addons/forum/Model/Topic.php
index dc72498..74491d1 100644
--- a/system/user/addons/forum/Model/Topic.php
+++ b/system/user/addons/forum/Model/Topic.php
@@ -167,8 +167,13 @@ public static function onBeforeBulkDelete($delete_ids)
 
     public static function onAfterBulkDelete($delete_ids)
     {
-        require_once PATH_ADDONS . 'forum/mod.forum.php';
-        require_once PATH_ADDONS . 'forum/mod.forum_core.php';
+        foreach(['forum/mod.forum.php', 'forum/mod.forum_core.php'] as $file) {
+            if (file_exists(PATH_THIRD . $file)) {
+                require_once PATH_THIRD . $file;
+            } else {
+                require_once PATH_ADDONS . $file;
+            }
+        }
 
         $forum_core = new \Forum_Core();
 
diff --git a/system/user/addons/forum/addon.setup.php b/system/user/addons/forum/addon.setup.php
index c0f69c5..620ba7b 100644
--- a/system/user/addons/forum/addon.setup.php
+++ b/system/user/addons/forum/addon.setup.php
@@ -5,7 +5,7 @@
     'author_url' => 'https://expressionengine.com/',
     'name' => 'Forum',
     'description' => 'Add a full-featured forum to your site',
-    'version' => '5.1.2',
+    'version' => '5.1.3',
     'namespace' => 'ExpressionEngine\Addons\Forum',
     'settings_exist' => true,
 
diff --git a/system/user/addons/forum/mod.forum.php b/system/user/addons/forum/mod.forum.php
index c326803..b8a6136 100644
--- a/system/user/addons/forum/mod.forum.php
+++ b/system/user/addons/forum/mod.forum.php
@@ -13,8 +13,8 @@
  */
 class Forum
 {
-    public $version = '5.1.2';
-    public $build = '20251119';
+    public $version = '5.1.3';
+    public $build = '20260305';
     public $use_site_profile = false;
     public $search_limit = 250; // Maximum number of search results (x2 since it can include this number of topics + this number of posts)
     public $return_data = '';
@@ -43,6 +43,7 @@ class Forum
     public $cur_thread_row = 0;
     public $thread_post_total = 0;	// Used for new entry submission to determine redirect page number
     public $trigger_error_page = false;
+    public $trigger_login_page = false;
     public $is_table_open = false;
     public $preview_override = false;
     public $mbr_class_loaded = false;
@@ -53,6 +54,7 @@ class Forum
     public $spellcheck_enabled = false;
     public $feeds_enabled = null;
     public $feed_ids = '';
+    public $date_limit = '';
     public $realm = "ExpressionEngine Forums";
     public $auth_attempt = false;
     public $use_sess_id = 0;	// Used in calls to ee()->functions->fetch_site_index() in certain URLs, like attachments
@@ -271,12 +273,12 @@ public function display_forum($function = '')
 
             // Parse Snippets
             foreach (ee()->config->_global_vars as $key => $val) {
-                $this->return_data = str_replace(LD . $key . RD, $val, $this->return_data);
+                $this->return_data = str_replace(LD . $key . RD, ($val === null) ? '' : $val, $this->return_data);
             }
 
             // Parse Global Variables
             foreach (ee()->TMPL->global_vars as $key => $val) {
-                $this->return_data = str_replace(LD . $key . RD, $val, $this->return_data);
+                $this->return_data = str_replace(LD . $key . RD, ($val === null) ? '' : $val, $this->return_data);
             }
 
             $this->return_data = $this->_final_prep($this->return_data);
@@ -938,7 +940,7 @@ public function var_swap($str, $data)
         }
 
         foreach ($data as $key => $val) {
-            $str = str_replace('{' . $key . '}', $val, $str);
+            $str = str_replace('{' . $key . '}', ($val === null) ? '' : $val, $str);
         }
 
         return $str;
diff --git a/system/user/addons/forum/mod.forum_core.php b/system/user/addons/forum/mod.forum_core.php
index 9a98f84..da1aeef 100644
--- a/system/user/addons/forum/mod.forum_core.php
+++ b/system/user/addons/forum/mod.forum_core.php
@@ -106,12 +106,12 @@ public function display_forum($function = '')
 
                 // Parse Snippets
                 foreach (ee()->config->_global_vars as $key => $val) {
-                    $this->return_data = str_replace(LD . $key . RD, $val, $this->return_data);
+                    $this->return_data = str_replace(LD . $key . RD, ($val === null) ? '' : $val, $this->return_data);
                 }
 
                 // Parse Global Variables
                 foreach (ee()->TMPL->global_vars as $key => $val) {
-                    $this->return_data = str_replace(LD . $key . RD, $val, $this->return_data);
+                    $this->return_data = str_replace(LD . $key . RD, ($val === null) ? '' : $val, $this->return_data);
                 }
 
                 $this->return_data = $this->_final_prep($this->return_data);
@@ -6180,7 +6180,8 @@ public function move_reply()
         }
 
         if (false !== (strpos($new_topic_id, "/"))) {
-            $new_topic_id = end(explode("/", $new_topic_id));
+            $new_topic_id_parts = explode("/", $new_topic_id);
+            $new_topic_id = end($new_topic_id_parts);
         }
 
         if (! is_numeric($new_topic_id)) {
@@ -6491,7 +6492,8 @@ public function do_merge()
         }
 
         if (false !== (strpos($merge_id, "/"))) {
-            $merge_id = end(explode("/", $merge_id));
+            $merge_id_parts = explode("/", $merge_id);
+            $merge_id = end($merge_id_parts);
         }
 
         if (! is_numeric($merge_id)) {
@@ -9523,7 +9525,7 @@ public function http_authentication_check_digest($allowed_groups = array())
         }
 
         // make sure Super Admins are always allowed
-        if (! in_array($allowed_groups, 1)) {
+        if (! in_array(1, $allowed_groups)) {
             $allowed_groups[] = 1;
         }
 
diff --git a/system/user/addons/forum/spam.forum.php b/system/user/addons/forum/spam.forum.php
index 55ebedb..8d79bff 100644
--- a/system/user/addons/forum/spam.forum.php
+++ b/system/user/addons/forum/spam.forum.php
@@ -20,8 +20,13 @@ class Forum_spam implements SpamModerationInterface
      */
     public function __construct()
     {
-        require_once PATH_ADDONS . 'forum/mod.forum.php';
-        require_once PATH_ADDONS . 'forum/mod.forum_core.php';
+        foreach(['forum/mod.forum.php', 'forum/mod.forum_core.php'] as $file) {
+            if (file_exists(PATH_THIRD . $file)) {
+                require_once PATH_THIRD . $file;
+            } else {
+                require_once PATH_ADDONS . $file;
+            }
+        }
 
         $this->fc = new \Forum_Core();
     }
diff --git a/system/user/addons/forum/tab.forum.php b/system/user/addons/forum/tab.forum.php
index 7f60d86..8d3daff 100644
--- a/system/user/addons/forum/tab.forum.php
+++ b/system/user/addons/forum/tab.forum.php
@@ -317,8 +317,13 @@ public function save($entry, $values)
 
                 // Update the forum stats
                 if (! class_exists('Forum')) {
-                    require PATH_ADDONS . 'forum/mod.forum.php';
-                    require PATH_ADDONS . 'forum/mod.forum_core.php';
+                    foreach(['forum/mod.forum.php', 'forum/mod.forum_core.php'] as $file) {
+                        if (file_exists(PATH_THIRD . $file)) {
+                            require_once PATH_THIRD . $file;
+                        } else {
+                            require_once PATH_ADDONS . $file;
+                        }
+                    }
                 }
 
                 $forum_core = new Forum_Core();