These days you can argue that a browser is intended to do anything, as there seems to be no scope limit to what goes into HTML5. But it's not what they're really about. Why did this exploit occur, well, WebCrypto apparently isn't directly exposed to WASM as C/C++ APIs even though that seems like an obvious thing to do. Or an even more obvious possibility: expose it as a subset of some existing API like POSIX. But WASM is api-lite, so everything beyond pure computation requires invoking JS and that's not how any existing C++ is written.
Eventually people will blast through this stuff. But, it was worked out in other platforms in the 80s and early 90s.
