I think it is clear what he means from the remainder of the blog post: I see a lot of people assert that safety issues (leading to exploitable bugs) It is obv

I think it is clear what he means from the remainder of the blog post: I see a lot of people assert that safety issues (leading to exploitable bugs) It is obvious that he is referring to typical C/C++ safety issues buffer overflows, use after free, etc. Even when dealing with Python arrays You can introduce security vulnerabilities in any programming language. But safe languages exclude a host of memory-related vulnerabilities, which are a substantial proportion of all vulnerabilities. Safety is not binary, some languages provide better safety or better means to model domain data safely than other languages.