Fix security vulnerability in admin modules

- The Module\BaseAdmin::post method checked credentials but didn't abort the process when it failed
- Created Module\BaseAdmin::checkAdminAccess method

src/Module/Admin/Addons/Details.php

@@ -32,7 +32,7 @@ class Details extends BaseAdmin
 {
 	public static function post(array $parameters = [])
 	{
-		parent::post($parameters);
+		self::checkAdminAccess();
 
 		$addon = Strings::sanitizeFilePathItem($parameters['addon']);