LiquidJS: ownPropertyOnly bypass for inherited array indices in first/last/join/reverse/slice/compact, `.first`/`.last`, negative index, and for-loop iteration

LiquidJS is a Shopify / GitHub Pages compatible template engine in pure JavaScript. Prior to 10.27.2, enabling ownPropertyOnly does not consistently restrict inherited array indices because negative indexing, .first, .last, the first filter, the last filter, join, reverse, slice, compact, and for-loop iteration can read prototype-provided elements outside readJSProperty(). An attacker who can influence prototype state or inherited array-index data and cause templates to render affected operations can disclose values that ownPropertyOnly is expected to hide. Direct positive indexing and ordinary object prototype reads are blocked, but the alternate array paths remain affected. This issue is fixed in 10.27.2.

Source published

6 Oct 2026 18:04:14 UTC

Source modified

9 Oct 2026 01:22:05 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 4.0 · 6.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N