fix(commons): skip prototype-polluting keys in _.merge#3690
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Object.keys() returns __proto__ as an own enumerable key for JSON-parsed sources, causing the recursive merge to write onto Object.prototype. Skip __proto__/constructor/prototype keys. Reported-by: Andrew Ridings (@ridingsa)
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Maybe a better alternative is https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty as this will never touch the prototype? Then we wouldn't need to add the exclusions?
https://claude.ai/share/609aae22-2720-40e6-8479-04e023e37776 Cc @ridingsa WDYT? |
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Summary
The recursive
_.mergehelper in@feathersjs/commonsiteratesObject.keys(source). When the source came fromJSON.parse('{"__proto__":...}'),__proto__is returned as an own-enumerable key, so the recursive call resolvestarget['__proto__']toObject.prototypeand writes onto it.This adds the standard guard to skip
__proto__,constructor, andprototypekeys during iteration.Changes
src/index.ts: skip the three prototype-mutating keys in the merge loop.test/utils.test.ts: regression test confirming a JSON-parsed__proto__/constructor.prototypesource no longer mutatesObject.prototype, fresh objects, or the target.Notes
mergestill works for all documented input shapes.Reported-by: Andrew Ridings (@ridingsa)