Comment by arbll

It used to be 100% runtime-level and it was the golden age of browser exploits. Each of your tabs are now a separate process that the OS sandboxes. They can only access a specific API over IPC for anything that goes beyond js/rendering (cookie management, etc...). An exploit in V8 today only gives access to this API. A second exploit is needed in this API to escape the sandbox and do anything meaningful on the target system.