LiquidJS: `{% render %}` tag silently bypasses per-render `ownPropertyOnly:true` via `Context.spawn()`

Summary

LiquidJS is a Shopify/GitHub Pages compatible template engine written in pure JavaScript. In versions 10.25.7 and below, Context.spawn() creates a child Context for the {% render %} tag but does not propagate the parent context's resolved ownPropertyOnly value, resulting in a silent bypass. The new context re-derives ownPropertyOnly from opts.ownPropertyOnly (the instance-level option), silently discarding any RenderOptions.ownPropertyOnly override that was supplied to parseAndRender(). As a result, a developer who runs a Liquid instance with the backwards-compatible ownPropertyOnly:false and then locks down an untrusted render with parseAndRender(..., { ownPropertyOnly: true }) still leaks prototype-chain properties from inside any {% render %} partial. This is a distinct exploit surface from the previously identified array-filter variants (where, reject, group_by, find, find_index, has) — the underlying root cause in Context.spawn() is shared, but {% render %} is a separately reachable sink that needs no filter usage. This issue has been fixed in version 10.26.0.

Timeline

1. Jun 17, 2026, 10:25 PM UTCCVE published
2. Jun 18, 2026, 1:45 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: yes · Technical impact: partial

3. Jun 18, 2026, 1:53 PM UTCRecord last updated

Affected versions

• harttle liquidjs

  fixed in 10.26.0

• liquidjsnpm

  fixed in 10.26.0

References 3