CVE-2026-44646
Summary
Context.spawn() in liquidjs creates a child Context for the {% render %} tag but does not propagate the parent context's resolved ownPropertyOnly value. 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.
Details
The bug is in Context.spawn():
// src/context/context.ts:105-114
public spawn (scope = {}) {
return new Context(scope, this.opts, {
sync: this.sync,
globals: this.globals,
strictVariables: this.strictVariables
// <-- ownPropertyOnly is missing here
}, {
renderLimit: this.renderLimit,
memoryLimit: this.memoryLimit
})
}
The constructor resolves ownPropertyOnly as:
// src/context/context.ts:47
this.ownPropertyOnly = renderOptions.ownPropertyOnly ?? opts.ownPropertyOnly
Because spawn() passes a RenderOptions object with no ownPropertyOnly, the child context falls back to opts.ownPropertyOnly (the instance-level option), throwing away any per-render override that the parent context had applied. this.opts is the raw normalized instance options object; it is not mutated to reflect render-time overrides.
The {% render %} tag at src/tags/render.ts:51-77 calls spawn() to build the partial's isolated scope:
- render (ctx: Context, emitter: Emitter): Generator<unknown, void, unknown> {
const { liquid, hash } = this
const filepath = (yield renderFilePath(this['file'], ctx, l
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Exploitation outlook
- Low exploitation risk0.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 19% of all EPSS-scored CVEs.
Advisory coverage (1)
External references
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