Doesn't really decrease any powers of a compromised process, but IPC bounds checks are generally a good idea. This prevents a debug assertion in fuzzers.
Created attachment 460377 [details] Patch
See rdar://82979527
Comment on attachment 460377 [details] Patch r=me
Committed r295719 (251724@main): <https://commits.webkit.org/251724@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 460377 [details].
<rdar://problem/95657318>
FWIW, the added `if` is actually dead code since bug 241547, as there are no callers with `i != index`. It's just an artefact of how the recursion for variadic templates is written. E.g. there's no fuzzer in the world that would've hit that assertion.