What is JavaScript JIT + WebAssembly? How does turning it off by default enhances privacy or security?

[spiralbee]

I wasn't able to login to some sites (webclient of email service) because of these being turned off.

What does turning off JavaScript JIT and Webassembly achieve?

Is it right for it to be off by default?

[Universalizer]

Is it right for it to be off by default?

Yes, turning it off by default enhances privacy or security.

https://github.com/bromite/bromite#site-settings

webGL, disabled by default
images, enabled by default
Javascript JIT, disabled by default
timezone customization override
autoplay, disabled by default
webRTC, disabled by default

For Wasm (Web assembly) check this following link
https://www.jit.io/blog/6-security-risks-to-consider-with-webassembly

[Darin755]

Web assembly is basicly like running a binary file on your computer. It is sandboxed but because of its binary nature it can do things like exploit CPU vulnerabilities.

The main reason its used us because it is very fast.