← WebKit Silent-Fix Report — 2026-W22

f181acea44  [JSC] `Array.prototype.join` skips prototype element added during element toString

severity low class LogicError confidence 0.40 JSC ArrayPrototype join
Sosuke Suzuki Sat May 30 02:10:07 2026 -0700 full: f181acea44641a3c7ebfc1181b0deaf049466d62 bug report ↗ view on GitHub ↗
Primitive: stale holesKnownToBeOK after element toString side effect
Triage note: Corrects handling of holes forwarding to prototype after a side effect; primarily an observable-correctness fix.

Security-relevant, below the exploitable-grade bar for a full root-cause writeup. The triage verdict is above; the side-by-side patch is below.

Before / after

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