Files
liquidjs/docs/source
457fae0736 fix(security): block Object.prototype filter/tag lookups (RCE) (#897)
* fix(security): block Object.prototype filter/tag lookups (RCE)

`liquid.filters` and `liquid.tags` were plain `{}` so bracket access on
template-controlled keys inherited from `Object.prototype`. Most damaging:
`{{ x | valueOf }}` resolved to `Object.prototype.valueOf`, which the
filter pipeline called as a handler with `this = FilterImpl`; valueOf
returns its receiver, leaking `context`, `liquid`, `token` (and via them
parser, loader, fs) into the template — chain that with `group_by`/`where`
gadgets and an attacker reaches `Function`/`child_process` for RCE.
Same shape on the tag side: `{% constructor %}` bypassed the
"tag not found" assertion and crashed with a confusing message.

Use null-prototype storage so `liquid.filters[name]` / `liquid.tags[name]`
only resolve to explicitly registered entries. The existing
`assert(impl || !strictFilters)` and `assert(TagClass, ...)` now do the
right thing for `valueOf`, `toString`, `constructor`, `__proto__`,
`hasOwnProperty`, `isPrototypeOf`, `__defineGetter__`, etc.

Co-authored-by: Cursor <[email protected]>

* test: fold prototype-registry regressions into register + e2e

Co-authored-by: Cursor <[email protected]>

* test: assert null-prototype registries vs all Object.prototype keys

Co-authored-by: Cursor <[email protected]>

* test: dedupe registry checks; merge filter prototype loop

Co-authored-by: Cursor <[email protected]>

* fix(context): use null-prototype scope and register objects

Add createScope(); use for bottom scope, spawn default, getAll merge, ctx.push frames, filter loops, include/layout blocks registers, and cycle groups. registers uses Object.create(null) and getRegister uses ??.

For-loop continue register defaults to 0 (not {}): Array.slice coerces plain {} but not null-prototype objects.

Export createScope from the package entry.

Co-authored-by: Cursor <[email protected]>

* revert(context): plain {} registers and getRegister ||

Registers are only mutated by tag implementations, not templates; keep null-prototype scopes/createScope for push frames.

Co-authored-by: Cursor <[email protected]>

* test(context): assert scope isolation without probing prototypes

Replace Object.getPrototypeOf checks for bottom() and getAll() with
'in' checks on typical Object.prototype names plus a merge assertion.

Co-authored-by: Cursor <[email protected]>

* test(e2e): assert constructor filter/tag lookups (node + UMD)

Co-authored-by: Cursor <[email protected]>

* test(context): cover Object.prototype keys under ownPropertyOnly

- Add getSync cases for constructor and valueOf on plain objects
- Remove scope storage tests that used the in operator

Co-authored-by: Cursor <[email protected]>

* refactor: remove createScope helper

Drop the exported helper and finish migrating call sites. Revert incidental context/for/include/layout churn so behavior matches mainline aside from the removal. Trim duplicate e2e and heavy Object.prototype loops in registry tests.

Co-authored-by: Cursor <[email protected]>

* docs: document ownPropertyOnly and Drop security in security model

Co-authored-by: Cursor <[email protected]>

* docs(zh-cn): sync security model with ownPropertyOnly and Drop notes

Co-authored-by: Cursor <[email protected]>

---------

Co-authored-by: Cursor <[email protected]>
2026-05-14 22:18:10 +08:00
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