One of the new features in Firefox 95 is component sandboxing in RLBox. The idea is to provide some level of protection across functional boundaries within the application. This is done by using WebAssembly to create a sandbox where modules can be called without exposing the memory space to attacks.
It’s an interesting concept and the documentation on the RLBox site describes it quite well. I haven’t used Firefox 95 for long, but it doesn’t seem to have had any deleterious effects.