WebAssembly, a newer type of “low-level” code that can be run by modern web browsers, is aimed at improving the web experience. The catch: Regular browsers execute such code locally. WebAssembly - merely a faster way for web-borne exploits to reach the local browser?
WebAssembly (WASM) is currently supported by major browsers including Firefox, Chrome, WebKit/Safari, and Microsoft Edge. Because the browser is running the WebAssembly code locally, any problems with that code also end up on the user’s machine and potentially pose a threat to the local IT environment.
How does WebAssembly work? WASM is not a high-level language. It is a way for language compilers (like those that read C, C++, and Rust high-level code) to express their assembly-level output in a different format. This output then can be directly executed by the browser.
Source: LogRocket Blog
By itself, WebAssembly code isn’t supposed to be able to do anything. It’s run inside a sandboxed virtual machine.