diff --git a/application/Espo/Core/Utils/Config.php b/application/Espo/Core/Utils/Config.php
index ecf8654a8b..f57daf7781 100644
--- a/application/Espo/Core/Utils/Config.php
+++ b/application/Espo/Core/Utils/Config.php
@@ -122,7 +122,11 @@ class Config
                 return $default;
             }
 
-            if (!isset($lastBranch[$key])) {
+            if (is_array($lastBranch) && !isset($lastBranch[$key])) {
+                return $default;
+            }
+
+            if (is_object($lastBranch) && !property_exists($lastBranch, $key)) {
                 return $default;
             }
 
@@ -152,7 +156,11 @@ class Config
                 return false;
             }
 
-            if (!isset($lastBranch[$key])) {
+            if (is_array($lastBranch) && !isset($lastBranch[$key])) {
+                return false;
+            }
+
+            if (is_object($lastBranch) && !property_exists($lastBranch, $key)) {
                 return false;
             }
 
@@ -311,8 +319,13 @@ class Config
         $internalData = $this->fileManager->isFile($this->internalConfigPath) ?
             $this->fileManager->getPhpContents($this->internalConfigPath) : [];
 
-        $this->data = Util::merge($systemData, $data);
-        $this->data = Util::merge($this->data, $internalData);
+        /** @var array<string,mixed> */
+        $mergedData = Util::merge(
+            Util::merge($systemData, $data),
+            $internalData
+        );
+
+        $this->data = $mergedData;
 
         $this->internalParamList = array_keys($internalData);
 
diff --git a/application/Espo/Core/Utils/Crypt.php b/application/Espo/Core/Utils/Crypt.php
index 97f1e2159b..5717d481b8 100644
--- a/application/Espo/Core/Utils/Crypt.php
+++ b/application/Espo/Core/Utils/Crypt.php
@@ -64,7 +64,10 @@ class Crypt
                 throw new RuntimeException("openssl extension is not loaded.");
             }
 
-            $this->iv = openssl_random_pseudo_bytes(16);
+            /** @var string */
+            $iv = openssl_random_pseudo_bytes(16);
+
+            $this->iv = $iv;
         }
 
         return $this->iv;
@@ -93,9 +96,13 @@ class Crypt
             throw new RuntimeException("openssl extension is not loaded.");
         }
 
-        return trim(
-            openssl_decrypt($string, 'aes-256-cbc', $this->getKey(), OPENSSL_RAW_DATA, $iv)
-        );
+        $value = openssl_decrypt($string, 'aes-256-cbc', $this->getKey(), OPENSSL_RAW_DATA, $iv);
+
+        if ($value === false) {
+            throw new RuntimeException("OpenSSL decrypt failure.");
+        }
+
+        return trim($value);
     }
 
     public function generateKey(): string
diff --git a/application/Espo/Core/Utils/DataUtil.php b/application/Espo/Core/Utils/DataUtil.php
index ce2b89c3ac..a02ec84b93 100644
--- a/application/Espo/Core/Utils/DataUtil.php
+++ b/application/Espo/Core/Utils/DataUtil.php
@@ -117,9 +117,9 @@ class DataUtil
     }
 
     /**
-     * @param array<string,mixed> $data
+     * @param array<string|int,mixed>|\stdClass $data
      * @param mixed $needle
-     * @return array<string,mixed>
+     * @return array<string|int,mixed>|\stdClass
      */
     public static function unsetByValue(&$data, $needle)
     {
@@ -156,7 +156,7 @@ class DataUtil
      *
      * @param array<string,mixed>|\stdClass $data
      * @param array<string,mixed>|\stdClass $overrideData
-     * @return array<string,mixed>|\stdClass
+     * @return array<string|int,mixed>|\stdClass
      */
     public static function merge($data, $overrideData)
     {
@@ -196,6 +196,8 @@ class DataUtil
                 $data = [];
             }
 
+            /** @var array<string,mixed> $data */
+
             if (in_array($appendIdentifier, $overrideData)) {
                 foreach ($overrideData as $key => $item) {
                     if ($item === $appendIdentifier) {
diff --git a/tests/unit/Espo/Core/Utils/ConfigTest.php b/tests/unit/Espo/Core/Utils/ConfigTest.php
index ce58f15d77..0c7db57fe0 100644
--- a/tests/unit/Espo/Core/Utils/ConfigTest.php
+++ b/tests/unit/Espo/Core/Utils/ConfigTest.php
@@ -36,6 +36,8 @@ use Espo\Core\Utils\Config\ConfigFileManager;
 
 class ConfigTest extends \PHPUnit\Framework\TestCase
 {
+    private ?Config $config = null;
+
     private $defaultTestConfig = 'tests/unit/testData/Utils/Config/config.php';
 
     private $configPath = 'tests/unit/testData/cache/config.php';
@@ -44,7 +46,7 @@ class ConfigTest extends \PHPUnit\Framework\TestCase
 
     private $internalConfigPath = 'tests/unit/testData/cache/config-internal.php';
 
-    protected function setUp() : void
+    protected function setUp(): void
     {
         $this->fileManager = new ConfigFileManager;
 
@@ -74,7 +76,7 @@ class ConfigTest extends \PHPUnit\Framework\TestCase
         $this->assertArrayHasKey('dateFormat', $this->reflection->invokeMethod('getData', []));
     }
 
-    public function testGet()
+    public function testGet1(): void
     {
         $result = [
             'driver' => 'pdo_mysql',
@@ -108,7 +110,7 @@ class ConfigTest extends \PHPUnit\Framework\TestCase
         $this->assertArrayHasKey('adminItems', $configData);
     }
 
-    public function testGet1(): void
+    public function testGet2(): void
     {
         $fileManager = $this->createMock(ConfigFileManager::class);
 
@@ -157,4 +159,55 @@ class ConfigTest extends \PHPUnit\Framework\TestCase
             $config->getAllNonInternalData(),
         );
     }
+
+    public function testGet3(): void
+    {
+        $fileManager = $this->createMock(ConfigFileManager::class);
+
+        $fileManager
+            ->method('isFile')
+            ->willReturn(true);
+
+        $data = [
+            'a' => [
+                '1' => 'a1',
+            ],
+            'b' => (object) [
+                '1' => 'b1',
+            ],
+            'c' => 'c',
+            'd' => ['d'],
+        ];
+
+        $dataInternal = [
+        ];
+
+        $dataSystem = [
+        ];
+
+        $fileManager
+            ->method('getPhpContents')
+            ->will(
+                $this->returnValueMap([
+                    ['data/config.php', $data],
+                    ['data/config-internal.php', $dataInternal],
+                    ['application/Espo/Resources/defaults/systemConfig.php', $dataSystem],
+                ])
+            );
+
+
+        $config = new Config($fileManager);
+
+        $this->assertEquals(['1' => 'a1'], $config->get('a'));
+        $this->assertEquals('a1', $config->get('a.1'));
+        $this->assertEquals('b1', $config->get('b.1'));
+        $this->assertEquals('c', $config->get('c'));
+        $this->assertEquals(['d'], $config->get('d'));
+
+        $this->assertFalse($config->has('a.2'));
+        $this->assertTrue($config->has('a.1'));
+
+        $this->assertTrue($config->has('a'));
+        $this->assertFalse($config->has('0'));
+    }
 }