fix(store): harden setState against prototype pollution#1
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afiiif merged 1 commit intoafiiif:mainfrom Apr 13, 2026
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The change-detection loop in `setState` used `for...in` over the
incoming partial, which walks the full prototype chain. Any enumerable
property inherited from `Object.prototype` (whether introduced by a
polluted global, a faulty polyfill, or an untrusted payload parsed into
the call site) would be treated as a legitimate state key, pushed into
`changedKeys`, and forwarded to subscribers. Downstream consumers
tracking those keys via the proxy-based `useStore` hook would then
observe phantom updates for fields the caller never actually set.
Replace the iteration with `Object.keys(newValue)` so only own
enumerable string keys participate in the shallow diff, and explicitly
skip `__proto__`, `constructor`, and `prototype` as defense-in-depth
against payloads (e.g. `JSON.parse` output) where these names appear as
own properties. The subsequent `{ ...prevState, ...newValue }` merge is
already safe because object spread uses `CreateDataProperty` semantics,
but filtering upstream keeps the dangerous keys from ever reaching
`changedKeys` or the subscriber notification path.
Behaviour is unchanged for well-formed state objects: `Object.keys`
enumerates the same own keys `for...in` did, with no measurable perf
impact. Full test suite (90 tests) passes.
RakulAgn
commented
Apr 13, 2026
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Nice! 🙌 Thanks @RakulAgn |
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Have you Checked the Email and Concept |
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The change-detection loop in
setStateusedfor...inover the incoming partial, which walks the full prototype chain. Any enumerable property inherited fromObject.prototype(whether introduced by a polluted global, a faulty polyfill, or an untrusted payload parsed into the call site) would be treated as a legitimate state key, pushed intochangedKeys, and forwarded to subscribers. Downstream consumers tracking those keys via the proxy-baseduseStorehook would then observe phantom updates for fields the caller never actually set.Replace the iteration with
Object.keys(newValue)so only own enumerable string keys participate in the shallow diff, and explicitly skip__proto__,constructor, andprototypeas defense-in-depth against payloads (e.g.JSON.parseoutput) where these names appear as own properties. The subsequent{ ...prevState, ...newValue }merge is already safe because object spread usesCreateDataPropertysemantics, but filtering upstream keeps the dangerous keys from ever reachingchangedKeysor the subscriber notification path.Behaviour is unchanged for well-formed state objects:
Object.keysenumerates the same own keysfor...indid, with no measurable perf impact. Full test suite (90 tests) passes.