All payment is handled by our partner stripe. Find more about stripe's security terms here: https://stripe.com/docs/security.
During the payment process, all data are encrypted using HTTPS. Because HTTPS requires end-to-end encryption only the server and the client have the ability to decrypt the data. If any third party may be able to break the encryption were unable to read the data because the decryption key is not transferred with the data at all.
Additionally payment via stripe requires HTTP Strict Transport Security (HSTS). This means that the server forces the client to only use secured connections for the duration of the data transfer. Otherwise a data transfer is not possible.
To increase the level of security for your payment data even further we do not save any of your payment information on our server or in our system.
Although this means that you will have to enter your payment information every time you want to upgrade your plan, we achieve a higher level of security.