For a small/medium-sized project WordPress might be acceptable. However, if you plan to scale up and expect a lot of traffic it will be quite difficult to keep up.

Security of WP has improved in recent years, however, it still relies in PHP one of the languages that historically has suffered of prevalent security issues.

Scalability will be difficult at some point, you will need professional infrastructure to get a lot of transactions and other operations smooth. I would recommend research dedicated eCommerce platforms, remember Wordpress was originally conceived as a blogging platform.