diff --git a/exec/lib/BackupQueueService.php b/exec/lib/BackupQueueService.php
index bc36136..405746e 100644
--- a/exec/lib/BackupQueueService.php
+++ b/exec/lib/BackupQueueService.php
@@ -437,10 +437,12 @@ final class BackupQueueService
             throw new RuntimeException('Nie można odczytać przesłanego pliku backupu.');
         }
 
+        // Security: never trust $uploadReference as a literal path - it comes
+        // straight from user-controlled POST data, and this whole plugin runs
+        // as root. Only accept a file whose *basename* matches one of the
+        // known DirectAdmin/system temp directories below, never an
+        // arbitrary absolute path chosen by the caller.
         $sourceCandidates = [];
-        if (str_starts_with($uploadReference, '/') && is_file($uploadReference)) {
-            $sourceCandidates[] = $uploadReference;
-        }
         $tmpDirs = [
             (string)(getenv('UPLOAD_TMP_DIR') ?: ''),
             (string)(getenv('DA_UPLOAD_TMP_DIR') ?: ''),
diff --git a/tests/backup_restore_upload_path_test.php b/tests/backup_restore_upload_path_test.php
new file mode 100644
index 0000000..7bc6efa
--- /dev/null
+++ b/tests/backup_restore_upload_path_test.php
@@ -0,0 +1,96 @@
+<?php
+declare(strict_types=1);
+
+$pluginTempRoot = sys_get_temp_dir() . '/altmysql-plugin-root-' . bin2hex(random_bytes(4));
+mkdir($pluginTempRoot, 0700, true);
+define('PLUGIN_ROOT', $pluginTempRoot);
+
+$pluginDir = dirname(__DIR__);
+require_once $pluginDir . '/exec/lib/Settings.php';
+require_once $pluginDir . '/exec/lib/DirectAdminUser.php';
+require_once $pluginDir . '/exec/lib/BackupQueueService.php';
+
+function fail(string $message): void
+{
+    fwrite(STDERR, "FAIL: {$message}\n");
+    exit(1);
+}
+
+function assert_true(bool $condition, string $message): void
+{
+    if (!$condition) {
+        fail($message);
+    }
+}
+
+function load_settings(string $contents): Settings
+{
+    $path = tempnam(sys_get_temp_dir(), 'altmysql-settings-');
+    if ($path === false) {
+        fail('cannot create temp settings file');
+    }
+    file_put_contents($path, $contents);
+    $settings = Settings::load($path);
+    unlink($path);
+    return $settings;
+}
+
+function make_da_user(Settings $settings, string $username): DirectAdminUser
+{
+    $class = new ReflectionClass(DirectAdminUser::class);
+    /** @var DirectAdminUser $user */
+    $user = $class->newInstanceWithoutConstructor();
+    foreach ([
+        'username' => $username,
+        'prefix' => $username . '_',
+        'userConf' => [],
+        'packageConf' => [],
+        'settings' => $settings,
+    ] as $property => $value) {
+        $prop = $class->getProperty($property);
+        $prop->setAccessible(true);
+        $prop->setValue($user, $value);
+    }
+    return $user;
+}
+
+$settings = load_settings('');
+$daUser = make_da_user($settings, 'demo');
+$queue = new BackupQueueService($settings, $daUser);
+
+// A path outside every recognized DirectAdmin/system temp directory must be
+// rejected, even if it exists and is readable - it must not be treated as a
+// legitimate upload reference just because the caller supplied it verbatim.
+$secretDir = sys_get_temp_dir() . '/altmysql-secret-' . bin2hex(random_bytes(4));
+mkdir($secretDir, 0700, true);
+$secretFile = $secretDir . '/secret_credentials.sql';
+file_put_contents($secretFile, 'SECRET CONTENT THAT MUST NEVER BE COPIED');
+
+$threw = false;
+try {
+    $queue->stageRestoreUploadFromDirectAdminTemp($secretFile, 'harmless.sql');
+} catch (Throwable $e) {
+    $threw = true;
+}
+assert_true($threw, 'a path outside the known DirectAdmin/system temp directories must be rejected, not staged');
+
+// A legitimate reference - a file that DirectAdmin actually placed directly
+// inside a recognized temp directory - must still work.
+$legitFile = sys_get_temp_dir() . '/altmysql-da-upload-' . bin2hex(random_bytes(4)) . '.sql';
+file_put_contents($legitFile, 'SELECT 1;');
+
+$stagedPath = $queue->stageRestoreUploadFromDirectAdminTemp($legitFile, 'legit.sql');
+assert_true(is_file($stagedPath), 'a file directly inside a recognized temp directory must still be staged');
+assert_true(
+    trim((string)file_get_contents($stagedPath)) === 'SELECT 1;',
+    'the staged file must contain the legitimate source content'
+);
+
+// cleanup
+@unlink($secretFile);
+@rmdir($secretDir);
+@unlink($legitFile);
+@unlink($stagedPath);
+exec('rm -rf ' . escapeshellarg($pluginTempRoot));
+
+echo "backup_restore_upload_path_test: OK\n";