The short answer is: super secure.
We take security, privacy and confidentiality very seriously. We use the same levels of encryption security that banks do to protect consumers data over the web (SSL 256bit). Your data is confidential and nobody can access your account or even your credentials.
In regards to payments, we are PCI compliant, which means that all your billing data is 100% secure and not stored locally but rather on the payment gateway servers which are the safest place for them.