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

Why it is Yellow

• CVSS 6.0 medium
• Public exploit or proof of concept referenced
• On your watchlist: npm

Affected packages

References

• https://github.com/advisories/GHSA-fwxr-j5w2-587m
• https://github.com/harttle/liquidjs/security/advisories/GHSA-fwxr-j5w2-587m
• https://nvd.nist.gov/vuln/detail/CVE-2026-106120
• https://github.com/harttle/liquidjs/pull/924
• https://github.com/harttle/liquidjs/commit/552819a84b80c62306fe61072628a756272dc749
• https://github.com/harttle/liquidjs/releases/tag/v10.27.2
• https://github.com/advisories/GHSA-fwxr-j5w2-587m

Original 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.