It's a spectrum. JIT is inherently insecure, but is "secure enough" given other guards. We use it because it's fast, at the added risk. We can infact make thing

It's a spectrum. JIT is inherently insecure, but is "secure enough" given other guards. We use it because it's fast, at the added risk. We can infact make things provably safe within certain contexts. But we don't, because it's hard, and it can never perform as well. Wasms safety is dependent upon the runtime implementation, not the language. "Fast" is a motivation in web. If it renders slow, it loses money. We have 20 years of hacky methods to make JavaScript fast. These lead to security flaws.