> AND the attacker can correctly guess the memory layout AMD has several unpatched vulnerabilities that leak the memory layout/page table mappings, effectively

> AND the attacker can correctly guess the memory layout AMD has several unpatched vulnerabilities that leak the memory layout/page table mappings, effectively nullifying KASLR as well. they can be mitigated by KPTI, but AMD ships that in a disabled state by default because of the performance implications (with ryzen's reliance on giant caches, flushing caches every time they make a syscall would be even more disastrous for them than for Intel, so they cheat and ship insecure-by-default). The rest of that sentence is just an overwrought description of running a javascript segment in a web browser, there's nothing load-bearing there to prevent an attack.