OneBox Security

It is necessary to clarify the question of what exactly the client means.
If the question is about data encryption between the client and the server - we use HTTP (SSL) encryption.
The SSL security certificate is bought by whichever client wants. By default, we use Lets Encrypt.
If the question is about "did the OneBox system pass a security audit" - yes, a couple of years ago from a third-party company. This is purely our internal trouble so that we can be sure that everything is ok with the software. Didn't get any certificates. We just ordered an audit service under a contract - we received a list of bugs and fixed them.
If the question is about "is OneBox certified as software for some industry" - then the answer is "no", because this is not a mandatory procedure.
Such certification is needed only for certain regions with certain software topics. For example, if you build a billing system for telecommunications providers in the Russian Federation.
In reality, obtaining this certificate looks like "pay some money - we will enter you into the registry, but what kind of software is there - we don't care."