[112233]

Yes it is not safe. Just because you do not access undefined memory in an untyped GC language like javascript or python does not mean you can enforce that program invariants are maintained. You still get resource leaks, races, corruption etc. just without a crash (which makes it arguably worse because the defect is not immedeately apparent) Encoding program invariants cannot have "correct" solution, because you must balance expressivenes with compile time decidability.

[kaba0]

Both JS and python are safe from races and corruption, unless you very explicitly go out of your way. JS has no parallelism, and python has the GIL.

Leaks are not a security concern (besides DOS attacks).