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

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

• liquidjs 10.27.2Fixed version · GitHub Advisories · npm package liquidjs: upgrade to 10.27.2 or later (affected <= 10.27.1)

[ Packages ]Affected open-source packages

• liquidjs npmAffected <= 10.27.1 · fixed in 10.27.2 · GHSA-fwxr-j5w2-587m

[ References ]References

• github.com/harttle/liquidjs/commit/552819a84b80c62306fe61072628a756272dc749
• github.com/harttle/liquidjs/pull/924
• github.com/harttle/liquidjs/releases/tag/v10.27.2
• github.com/harttle/liquidjs/security/advisories/GHSA-fwxr-j5w2-587m