Almost every "call" is potentially dangerous. Asking for a language or a dialect of an existing language without potentially dangerous calls will leave you with nothing, hence the lack of answers from the people you contacted. It is up to you to find out what weaknesses a language has and how to either overcome them or, if to cumbersome, avoid the language altogether.
Then you also have to take into account the security issues the system running your software may have. Windows has quite the "rap sheet", when it comes to vulnerabilities. But still it is a solid OS to run your software on, if you are aware of these issues. You may choose to run in a browser...that in itself may expose you to new risks you'll have to learn about, risks that may even be specific to the OS running the browser, so you'll end up checking out combinations of browsers and OSes even over different versions, a ton of permutations to evaluate. And so far you haven't even looked at hardware. What about the USB ports on a standard PC? How can you verify that they are not misused? As you see cyber security is very expensive, thinking about what might go wrong is just the first step of many. Real security however is just an illusion, just like the idea of error free software. What you need to have is risk assessment together with a catalog of countermeasures and assess how useful or indispensable your software really may be. If the benefit-risk-ratio is acceptable, go ahead build your software, if not... I seem to have drifted of, sorry.