That quote is talking about (untrusted) compilers that translate from C/C++ with undefined behavior to WebAssembly programs. The latter would still have a defin

That quote is talking about (untrusted) compilers that translate from C/C++ with undefined behavior to WebAssembly programs. The latter would still have a defined behavior. People already "hammer on the entire JavaScript API with invalid parameters". That's what fuzzing is, and yes, it does find implementation errors which can lead to security problems.