diff --git a/src/Controller/ActivityController.php b/src/Controller/ActivityController.php
index fe4948b6..f50d36be 100644
--- a/src/Controller/ActivityController.php
+++ b/src/Controller/ActivityController.php
@@ -17,6 +17,7 @@ use App\Entity\ActivityRate;
 use App\Entity\MetaTableTypeInterface;
 use App\Entity\Project;
 use App\Entity\Team;
+use App\Event\ActivityDetailControllerEvent;
 use App\Event\ActivityMetaDefinitionEvent;
 use App\Event\ActivityMetaDisplayEvent;
 use App\Export\Spreadsheet\EntityWithMetaFieldsExporter;
@@ -140,6 +141,11 @@ final class ActivityController extends AbstractController
             $teams = $activity->getTeams();
         }
 
+        // additional boxes by plugins
+        $event = new ActivityDetailControllerEvent($activity);
+        $this->dispatcher->dispatch($event);
+        $boxes = $event->getController();
+
         return $this->render('activity/details.html.twig', [
             'activity' => $activity,
             'stats' => $stats,
@@ -147,6 +153,7 @@ final class ActivityController extends AbstractController
             'team' => $defaultTeam,
             'teams' => $teams,
             'now' => $now,
+            'boxes' => $boxes
         ]);
     }
 
diff --git a/src/Controller/CustomerController.php b/src/Controller/CustomerController.php
index faefbeb7..4f33f83a 100644
--- a/src/Controller/CustomerController.php
+++ b/src/Controller/CustomerController.php
@@ -16,6 +16,7 @@ use App\Entity\CustomerComment;
 use App\Entity\CustomerRate;
 use App\Entity\MetaTableTypeInterface;
 use App\Entity\Team;
+use App\Event\CustomerDetailControllerEvent;
 use App\Event\CustomerMetaDefinitionEvent;
 use App\Event\CustomerMetaDisplayEvent;
 use App\Export\Spreadsheet\EntityWithMetaFieldsExporter;
@@ -300,7 +301,6 @@ final class CustomerController extends AbstractController
         $attachments = [];
         $comments = null;
         $teams = null;
-        $projects = null;
         $rates = [];
         $now = $this->getDateTimeFactory()->createDateTime();
 
@@ -331,6 +331,11 @@ final class CustomerController extends AbstractController
             $teams = $customer->getTeams();
         }
 
+        // additional boxes by plugins
+        $event = new CustomerDetailControllerEvent($customer);
+        $this->dispatcher->dispatch($event);
+        $boxes = $event->getController();
+
         return $this->render('customer/details.html.twig', [
             'customer' => $customer,
             'comments' => $comments,
@@ -342,6 +347,7 @@ final class CustomerController extends AbstractController
             'customer_now' => new \DateTime('now', $timezone),
             'rates' => $rates,
             'now' => $now,
+            'boxes' => $boxes
         ]);
     }
 
diff --git a/src/Controller/ProjectController.php b/src/Controller/ProjectController.php
index 75e21560..3902926c 100644
--- a/src/Controller/ProjectController.php
+++ b/src/Controller/ProjectController.php
@@ -17,6 +17,7 @@ use App\Entity\ProjectComment;
 use App\Entity\ProjectRate;
 use App\Entity\Rate;
 use App\Entity\Team;
+use App\Event\ProjectDetailControllerEvent;
 use App\Event\ProjectMetaDefinitionEvent;
 use App\Event\ProjectMetaDisplayEvent;
 use App\Export\Spreadsheet\EntityWithMetaFieldsExporter;
@@ -348,6 +349,11 @@ final class ProjectController extends AbstractController
             $teams = $project->getTeams();
         }
 
+        // additional boxes by plugins
+        $event = new ProjectDetailControllerEvent($project);
+        $this->dispatcher->dispatch($event);
+        $boxes = $event->getController();
+
         return $this->render('project/details.html.twig', [
             'project' => $project,
             'comments' => $comments,
@@ -358,6 +364,7 @@ final class ProjectController extends AbstractController
             'teams' => $teams,
             'rates' => $rates,
             'now' => $now,
+            'boxes' => $boxes
         ]);
     }
 
diff --git a/src/Event/ActivityDetailControllerEvent.php b/src/Event/ActivityDetailControllerEvent.php
new file mode 100644
index 00000000..4d3be7ff
--- /dev/null
+++ b/src/Event/ActivityDetailControllerEvent.php
@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Event;
+
+/**
+ * Triggered for activity detail pages, to add additional content boxes.
+ *
+ * @see https://symfony.com/doc/5.4/templates.html#embedding-controllers
+ */
+final class ActivityDetailControllerEvent extends AbstractActivityEvent
+{
+    private $controller = [];
+
+    public function addController(string $controller): void
+    {
+        $this->controller[] = $controller;
+    }
+
+    public function getController(): array
+    {
+        return $this->controller;
+    }
+}
diff --git a/src/Event/CustomerDetailControllerEvent.php b/src/Event/CustomerDetailControllerEvent.php
new file mode 100644
index 00000000..3b2b0f37
--- /dev/null
+++ b/src/Event/CustomerDetailControllerEvent.php
@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Event;
+
+/**
+ * Triggered for customer detail pages, to add additional content boxes.
+ *
+ * @see https://symfony.com/doc/5.4/templates.html#embedding-controllers
+ */
+final class CustomerDetailControllerEvent extends AbstractCustomerEvent
+{
+    private $controller = [];
+
+    public function addController(string $controller): void
+    {
+        $this->controller[] = $controller;
+    }
+
+    public function getController(): array
+    {
+        return $this->controller;
+    }
+}
diff --git a/src/Event/ProjectDetailControllerEvent.php b/src/Event/ProjectDetailControllerEvent.php
new file mode 100644
index 00000000..d2aafb32
--- /dev/null
+++ b/src/Event/ProjectDetailControllerEvent.php
@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Event;
+
+/**
+ * Triggered for project detail pages, to add additional content boxes.
+ *
+ * @see https://symfony.com/doc/5.4/templates.html#embedding-controllers
+ */
+final class ProjectDetailControllerEvent extends AbstractProjectEvent
+{
+    private $controller = [];
+
+    public function addController(string $controller): void
+    {
+        $this->controller[] = $controller;
+    }
+
+    public function getController(): array
+    {
+        return $this->controller;
+    }
+}
diff --git a/templates/activity/details.html.twig b/templates/activity/details.html.twig
index 8e1c56c0..c742cc33 100644
--- a/templates/activity/details.html.twig
+++ b/templates/activity/details.html.twig
@@ -93,6 +93,10 @@
         {{ include('embeds/budgets.html.twig', {'entity': activity, 'stats': stats, 'currency': currency}) }}
     {% endif %}
 
+    {% for controller in boxes %}
+        {{ render(controller(controller, {'activity': activity, 'page': 1})) }}
+    {% endfor %}
+
     {% if can_edit %}
         {{ include('embeds/rates-table.html.twig', {'id': 'activity_rates_box', 'entity': activity, 'create_url': path('admin_activity_rate_add', {'id': activity.id}), 'delete_route': 'delete_activity_rate', 'currency': currency}) }}
     {% endif %}
diff --git a/templates/customer/details.html.twig b/templates/customer/details.html.twig
index 653a822d..b007475a 100644
--- a/templates/customer/details.html.twig
+++ b/templates/customer/details.html.twig
@@ -132,6 +132,10 @@
         {{ include('embeds/budgets.html.twig', {'entity': customer, 'stats': stats, 'currency': customer.currency}) }}
     {% endif %}
 
+    {% for controller in boxes %}
+        {{ render(controller(controller, {'customer': customer, 'page': 1})) }}
+    {% endfor %}
+
     {% if can_edit %}
         {{ include('embeds/rates-table.html.twig', {'id': 'customer_rates_box', 'entity': customer, 'create_url': path('admin_customer_rate_add', {'id': customer.id}), 'delete_route': 'delete_customer_rate', 'currency': customer.currency}) }}
     {% endif %}
diff --git a/templates/project/details.html.twig b/templates/project/details.html.twig
index efb98712..3ec6543e 100644
--- a/templates/project/details.html.twig
+++ b/templates/project/details.html.twig
@@ -134,6 +134,10 @@
         {{ include('embeds/budgets.html.twig', {'entity': project, 'stats': stats, 'currency': project.customer.currency}) }}
     {% endif %}
 
+    {% for controller in boxes %}
+        {{ render(controller(controller, {'project': project, 'page': 1})) }}
+    {% endfor %}
+
     {% if can_edit %}
         {{ include('embeds/rates-table.html.twig', {'id': 'project_rates_box', 'entity': project, 'create_url': path('admin_project_rate_add', {'id': project.id}), 'delete_route': 'delete_project_rate', 'currency': project.customer.currency}) }}
     {% endif %}
diff --git a/tests/Event/ActivityDetailControllerEventTest.php b/tests/Event/ActivityDetailControllerEventTest.php
new file mode 100644
index 00000000..8f6770b7
--- /dev/null
+++ b/tests/Event/ActivityDetailControllerEventTest.php
@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\Event;
+
+use App\Entity\Activity;
+use App\Event\AbstractActivityEvent;
+use App\Event\ActivityDetailControllerEvent;
+
+/**
+ * @covers \App\Event\AbstractActivityEvent
+ * @covers \App\Event\ActivityDetailControllerEvent
+ */
+class ActivityDetailControllerEventTest extends AbstractActivityEventTest
+{
+    protected function createActivityEvent(Activity $activity): AbstractActivityEvent
+    {
+        return new ActivityDetailControllerEvent($activity);
+    }
+
+    public function testController(): void
+    {
+        /** @var ActivityDetailControllerEvent $event */
+        $event = $this->createActivityEvent(new Activity());
+        $event->addController('Foo\\Bar::helloWorld');
+        $this->assertEquals(['Foo\\Bar::helloWorld'], $event->getController());
+    }
+}
diff --git a/tests/Event/CustomerDetailControllerEventTest.php b/tests/Event/CustomerDetailControllerEventTest.php
new file mode 100644
index 00000000..acdb0412
--- /dev/null
+++ b/tests/Event/CustomerDetailControllerEventTest.php
@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\Event;
+
+use App\Entity\Customer;
+use App\Event\AbstractCustomerEvent;
+use App\Event\CustomerDetailControllerEvent;
+
+/**
+ * @covers \App\Event\AbstractCustomerEvent
+ * @covers \App\Event\CustomerDetailControllerEvent
+ */
+class CustomerDetailControllerEventTest extends AbstractCustomerEventTest
+{
+    protected function createCustomerEvent(Customer $customer): AbstractCustomerEvent
+    {
+        return new CustomerDetailControllerEvent($customer);
+    }
+
+    public function testController(): void
+    {
+        /** @var CustomerDetailControllerEvent $event */
+        $event = $this->createCustomerEvent(new Customer());
+        $event->addController('Foo\\Bar::helloWorld');
+        $this->assertEquals(['Foo\\Bar::helloWorld'], $event->getController());
+    }
+}
diff --git a/tests/Event/ProjectDetailControllerEventTest.php b/tests/Event/ProjectDetailControllerEventTest.php
new file mode 100644
index 00000000..dcab2812
--- /dev/null
+++ b/tests/Event/ProjectDetailControllerEventTest.php
@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\Event;
+
+use App\Entity\Project;
+use App\Event\AbstractProjectEvent;
+use App\Event\ProjectDetailControllerEvent;
+
+/**
+ * @covers \App\Event\AbstractProjectEvent
+ * @covers \App\Event\ProjectDetailControllerEvent
+ */
+class ProjectDetailControllerEventTest extends AbstractProjectEventTest
+{
+    protected function createProjectEvent(Project $project): AbstractProjectEvent
+    {
+        return new ProjectDetailControllerEvent($project);
+    }
+
+    public function testController(): void
+    {
+        /** @var ProjectDetailControllerEvent $event */
+        $event = $this->createProjectEvent(new Project());
+        $event->addController('Foo\\Bar::helloWorld');
+        $this->assertEquals(['Foo\\Bar::helloWorld'], $event->getController());
+    }
+}