diff --git a/app/assets/javascripts/app/controllers/_application_controller.coffee b/app/assets/javascripts/app/controllers/_application_controller.coffee
index 81918642e..acd02c1b9 100644
--- a/app/assets/javascripts/app/controllers/_application_controller.coffee
+++ b/app/assets/javascripts/app/controllers/_application_controller.coffee
@@ -249,11 +249,7 @@ class App.Controller extends Spine.Controller
     false
 
   permissionCheck: (key) ->
-    userId = App.Session.get('id')
-    return false if !userId
-    user = App.User.findNative(userId)
-    return false if !user
-    user.permission(key)
+    App.User.current()?.permission(key)
 
   authenticateCheckRedirect: ->
     return true if @authenticateCheck()
diff --git a/app/assets/javascripts/app/controllers/_application_controller_generic.coffee b/app/assets/javascripts/app/controllers/_application_controller_generic.coffee
index 6ce648472..f5c9a09a3 100644
--- a/app/assets/javascripts/app/controllers/_application_controller_generic.coffee
+++ b/app/assets/javascripts/app/controllers/_application_controller_generic.coffee
@@ -439,8 +439,6 @@ class App.ControllerNavSidbar extends App.Controller
     if @authenticateRequired
       @authenticateCheckRedirect()
 
-    @user = App.User.find(App.Session.get('id'))
-
     @render(true)
 
     @bind('ui:rerender',
@@ -501,7 +499,7 @@ class App.ControllerNavSidbar extends App.Controller
         else
           match = false
           for permissionName in item.permission
-            if !match && @user.permission(permissionName)
+            if !match && @permissionCheck(permissionName)
               match = true
               groupsUnsorted.push item
     _.sortBy(groupsUnsorted, (item) -> return item.prio)
@@ -520,7 +518,7 @@ class App.ControllerNavSidbar extends App.Controller
             else
               match = false
               for permissionName in item.permission
-                if !match && @user && @user.permission(permissionName)
+                if !match && @permissionCheck(permissionName)
                   match = true
                   itemsUnsorted.push item
 
diff --git a/app/assets/javascripts/app/controllers/agent_ticket_create/sidebar_customer.coffee b/app/assets/javascripts/app/controllers/agent_ticket_create/sidebar_customer.coffee
index 811e0013e..ea1171637 100644
--- a/app/assets/javascripts/app/controllers/agent_ticket_create/sidebar_customer.coffee
+++ b/app/assets/javascripts/app/controllers/agent_ticket_create/sidebar_customer.coffee
@@ -11,8 +11,7 @@ class SidebarCustomer extends App.Controller
     }
     if App.User.exists(@params.customer_id)
       customer = App.User.find(@params.customer_id)
-      currentUser = App.User.find(App.Session.get('id'))
-      if customer.isAccessibleBy(currentUser, 'change')
+      if customer.isAccessibleBy(App.User.current(), 'change')
         @item.sidebarActions.push {
           title:    'Edit Customer'
           name:     'customer-edit'
diff --git a/app/assets/javascripts/app/controllers/integrations.coffee b/app/assets/javascripts/app/controllers/integrations.coffee
index b47bb5bf2..996e6de51 100644
--- a/app/assets/javascripts/app/controllers/integrations.coffee
+++ b/app/assets/javascripts/app/controllers/integrations.coffee
@@ -33,8 +33,6 @@ class Index extends App.ControllerSubContent
   render: =>
     return if @initRender && @integration
 
-    @user = App.User.find(App.Session.get('id'))
-
     @initRender = true
     integrations = []
     for key, value of @integrationItems
@@ -44,7 +42,7 @@ class Index extends App.ControllerSubContent
       else
         match = false
         for permissionName in value.permission
-          if !match && @user.permission(permissionName)
+          if !match && @permissionCheck(permissionName)
             match = true
             value.key = key
             integrations.push value
diff --git a/app/assets/javascripts/app/controllers/navigation.coffee b/app/assets/javascripts/app/controllers/navigation.coffee
index 6f11e4507..512b58fd4 100644
--- a/app/assets/javascripts/app/controllers/navigation.coffee
+++ b/app/assets/javascripts/app/controllers/navigation.coffee
@@ -312,7 +312,7 @@ class App.Navigation extends App.ControllerWidgetPermanent
     @searchContainer.addClass('open')
     @globalSearch.search(query: @query)
 
-  filterNavbar: (values, user, parent = null) ->
+  filterNavbar: (values, parent = null) ->
     return _.filter values, (item) =>
       if typeof item.callback is 'function'
         data = item.callback() || {}
@@ -320,16 +320,16 @@ class App.Navigation extends App.ControllerWidgetPermanent
           item[key] = value
 
       if !parent? && !item.parent || item.parent is parent
-        return @filterNavbarPermissionOk(item, user) &&
+        return @filterNavbarPermissionOk(item) &&
           @filterNavbarSettingOk(item)
       else
         return false
 
-  filterNavbarPermissionOk: (item, user) ->
+  filterNavbarPermissionOk: (item) ->
     return true unless item.permission
 
-    return _.any item.permission, (permissionName) ->
-      return user && user.permission(permissionName)
+    return _.any item.permission, (permissionName) =>
+      return @permissionCheck(permissionName)
 
   filterNavbarSettingOk: (item) ->
     return true unless item.setting
@@ -343,15 +343,11 @@ class App.Navigation extends App.ControllerWidgetPermanent
     level1 = []
     dropdown = {}
 
-    user = undefined
-    if App.Session.get('id')
-      user = App.User.find(App.Session.get('id'))
-
-    level1 = @filterNavbar(navbar, user)
+    level1 = @filterNavbar(navbar)
 
     for item in navbar
       if item.parent && !dropdown[ item.parent ]
-        dropdown[ item.parent ] = @filterNavbar(navbar, user, item.parent)
+        dropdown[ item.parent ] = @filterNavbar(navbar, item.parent)
 
         for itemLevel1 in level1
           if itemLevel1.target is item.parent
diff --git a/app/assets/javascripts/app/controllers/ticket_zoom/article_action/delete.coffee b/app/assets/javascripts/app/controllers/ticket_zoom/article_action/delete.coffee
index 7436c15f6..830f10c2b 100644
--- a/app/assets/javascripts/app/controllers/ticket_zoom/article_action/delete.coffee
+++ b/app/assets/javascripts/app/controllers/ticket_zoom/article_action/delete.coffee
@@ -3,16 +3,13 @@ class Delete
     return actions if ui.permissionCheck('ticket.customer')
 
     if article.type.name is 'note'
-      user = undefined
-      if App.Session.get('id') == article.created_by_id
-        user = App.User.find(App.Session.get('id'))
-        if user.permission('ticket.agent')
-          actions.push {
-            name: 'delete'
-            type: 'delete'
-            icon: 'trash'
-            href: '#'
-          }
+      if App.User.current()?.id == article.created_by_id && ui.permissionCheck('ticket.agent')
+        actions.push {
+          name: 'delete'
+          type: 'delete'
+          icon: 'trash'
+          href: '#'
+        }
 
     actions
 
diff --git a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_customer.coffee b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_customer.coffee
index 239b36105..6189ea78a 100644
--- a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_customer.coffee
+++ b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_customer.coffee
@@ -15,10 +15,11 @@ class SidebarCustomer extends App.Controller
       ]
     }
     return @item if @ticket && @ticket.customer_id == 1
-    currentUser = App.User.find(App.Session.get('id'))
+
+    # prevent exceptions if customer model is no available
     if @ticket.customer_id && App.User.exists(@ticket.customer_id)
       customer = App.User.find(@ticket.customer_id)
-      if customer.isAccessibleBy(currentUser, 'change')
+      if customer?.isAccessibleBy(App.User.current(), 'change')
         @item.sidebarActions.push {
           title:    'Edit Customer'
           name:     'customer-edit'
diff --git a/app/assets/javascripts/app/controllers/user_profile.coffee b/app/assets/javascripts/app/controllers/user_profile.coffee
index 3a2614c72..7653d6a2a 100644
--- a/app/assets/javascripts/app/controllers/user_profile.coffee
+++ b/app/assets/javascripts/app/controllers/user_profile.coffee
@@ -107,8 +107,6 @@ class ActionRow extends App.ObserverActionRow
     @navigate("ticket/create/customer/#{user.id}")
 
   actions: (user) =>
-    currentUser = App.User.find(App.Session.get('id'))
-
     actions = [
       {
         name:     'history'
@@ -122,7 +120,7 @@ class ActionRow extends App.ObserverActionRow
       }
     ]
 
-    if user.isAccessibleBy(currentUser, 'change')
+    if user.isAccessibleBy(App.User.current(), 'change')
       actions.unshift {
         name:     'edit'
         title:    'Edit'
diff --git a/app/assets/javascripts/app/controllers/widget/user_signup_check.coffee b/app/assets/javascripts/app/controllers/widget/user_signup_check.coffee
index d1f69529c..e42e3ba6d 100644
--- a/app/assets/javascripts/app/controllers/widget/user_signup_check.coffee
+++ b/app/assets/javascripts/app/controllers/widget/user_signup_check.coffee
@@ -12,9 +12,8 @@ class Widget extends App.Controller
       @verifyLater(user.id)
       'user_signup_verify'
     )
-    currentUserId = App.Session.get('id')
-    return if !currentUserId
-    @verifyLater(currentUserId)
+    user = App.User.current()
+    @verifyLater(user.id) if user?
 
   verifyLater: (userId) =>
     delay = =>
diff --git a/app/assets/javascripts/app/lib/app_post/task_manager.coffee b/app/assets/javascripts/app/lib/app_post/task_manager.coffee
index 6dcd1c987..152ec2db8 100644
--- a/app/assets/javascripts/app/lib/app_post/task_manager.coffee
+++ b/app/assets/javascripts/app/lib/app_post/task_manager.coffee
@@ -651,15 +651,11 @@ class _taskManagerSingleton extends App.Controller
     App.Event.trigger 'taskbar:init'
 
     # initial load of permanent tasks
-    user_id = App.Session.get('id')
-    user = undefined
-    if user_id
-      user = App.User.find(user_id)
     permanentTask  = App.Config.get('permanentTask')
     taskCount     = 0
     if permanentTask
       for key, config of permanentTask
-        if !config.permission || (user && user.permission(config.permission))
+        if !config.permission || @permissionCheck(config.permission)
           taskCount += 1
           do (key, config, taskCount) =>
             App.Delay.set(
diff --git a/app/assets/javascripts/app/models/ticket.coffee b/app/assets/javascripts/app/models/ticket.coffee
index 0b72415e3..6cfc91de0 100644
--- a/app/assets/javascripts/app/models/ticket.coffee
+++ b/app/assets/javascripts/app/models/ticket.coffee
@@ -247,10 +247,10 @@ class App.Ticket extends App.Model
     result
 
   editable: (permission = 'change') ->
-    user_id = App.Session.get('id')
-    return true if user_id is @customer_id
-    return false if !App.User.exists(user_id)
-    group_ids = App.User.find(user_id).allGroupIds(permission)
+    user = App.User.current()
+    return false if !user?
+    return true if user.id is @customer_id
+    group_ids = user.allGroupIds(permission)
     for local_group_id in group_ids
       if local_group_id.toString() is @group_id.toString()
         return true
diff --git a/app/assets/javascripts/app/models/user.coffee b/app/assets/javascripts/app/models/user.coffee
index 5ce2b6d85..31578811d 100644
--- a/app/assets/javascripts/app/models/user.coffee
+++ b/app/assets/javascripts/app/models/user.coffee
@@ -346,3 +346,7 @@ class App.User extends App.Model
     return false if @organization_id is null
     return false if requester.organization_id is null
     @organization_id == requester.organization_id
+
+  # Do NOT modify the return value of this method!
+  # It is a direct reference to a value in the App.User.irecords object.
+  @current: App.Session.get
diff --git a/public/assets/tests/session.js b/public/assets/tests/session.js
index e31eff281..0e166eefd 100644
--- a/public/assets/tests/session.js
+++ b/public/assets/tests/session.js
@@ -2,7 +2,8 @@ window.onload = function() {
 
 test('test current user behaviour by updating session user via assets', function() {
 
-  // load user
+  // Wenn App.User updated through asset and set as session user
+  //   expect App.Session.get with new values
   App.User.refresh([{
     "login": "hh@example.com",
     "firstname": "Harald",
@@ -18,11 +19,7 @@ test('test current user behaviour by updating session user via assets', function
     "asdf": "",
     "id": 6
   }]);
-
-  // set session user
   App.Session.set(6)
-
-  // verify attributes
   equal(App.Session.get('id'), 6)
   equal(App.Session.get('login'), 'hh@example.com')
   equal(App.Session.get('vip'), false)
@@ -32,7 +29,8 @@ test('test current user behaviour by updating session user via assets', function
   equal(App.Session.get().custom_key, undefined)
   equal(App.Session.get().not_existing, undefined)
 
-  // update session user via assets
+  // Wenn App.User updated through asset
+  //   expect App.Session.get with new values
   App.User.refresh([{
     "login": "hh_new@example.com",
     "firstname": "Harald",
@@ -48,8 +46,6 @@ test('test current user behaviour by updating session user via assets', function
     "asdf": "",
     "id": 6
   }]);
-
-  // verify attributes
   equal(App.Session.get('id'), 6)
   equal(App.Session.get('login'), 'hh_new@example.com')
   equal(App.Session.get('vip'), false)
@@ -59,7 +55,8 @@ test('test current user behaviour by updating session user via assets', function
   equal(App.Session.get().custom_key, undefined)
   equal(App.Session.get().not_existing, undefined)
 
-  // clear session
+  // Wenn App.Session is reseted to inital
+  //   expect undefined for all
   App.Session.init()
   equal(App.Session.get(), undefined)
   equal(App.Session.get('id'), undefined)
@@ -67,6 +64,19 @@ test('test current user behaviour by updating session user via assets', function
   equal(App.Session.get('vip'), undefined)
   equal(App.Session.get('custom_key'), undefined)
 
+  // When App.Session is set and set to undefined or null,
+  //   expect @current() to return null
+  App.Session.set(6)
+  App.Session.set(undefined)
+  equal(App.User.current(), null, 'with no active session')
+  App.Session.set(null)
+  equal(App.User.current(), null, 'with no active session')
+
+  // When App.Session is set with an invalid (not existing) user ID,
+  //   expect @current() to return null
+  App.Session.set(100)
+  equal(App.User.current(), null, 'with invalid session user ID')
+
 });
 
 }
\ No newline at end of file