There are many CMS detection methods, as for cmseek detects CMS via the following.
CMSeek has a modular bruteforce system meaning you can add your custom made bruteforce modules to work with cmseek. A proper documentation for creating modules will be created shortly but in case you already figured out how to (pretty easy once you analyze the pre-made modules)
Magento is an open-source e-commerce platform written in PHP. The software was originally developed by Varien, Inc, a US private company headquartered in Culver City, California, with assistance from volunteers
WordPress is a content management system based on PHP and MySQL that is usually used with the MySQL or MariaDB database servers but can also use the SQLite database engine. Features include a plugin architecture and a template system