The reason you can focus auditing on the second process is because you have a security architecture that enables that. Of course the security mechanisms you’re relying on there need to be exercised and occasionally fall apart too (meltdown, MDS, etc.).

Process isolation is not the only tool that you have to build a secure architecture. In this case, capabilities are still being limited by available FDs in the first process (as well as seccomp and the noting namespacing and file system controls), and access to FDs is still mediated by the second process. There is no such thing as “being able to take access away … to a file that was already opened” as this is simple not part of the threat model or security model being provided. You still need to be diligent about these security mechanisms as well.

The idea that Google has given up and just does fuzzing is nonsense. Fuzzing is a great tool, and has become more common and standardized — that’s all. It is being added to the full suite of tools.