Different Intel and AMD processors are affected by both primitives as shown in the affected processors' section. Regarding FPVI, our Firefox exploit works only on Intel CPUs with Firefox < 87.0. Regarding SCSB, we found several candidate gadgets in real-world code, but none of them was ultimately exploitable due to the coincidental presence of some serializing instruction preventing stale code execution. Nonetheless, mitigations are needed to enforce security-by-design. Indeed, the Xen hypervisor mitigated SCSB following our proposed mitigation.