Prototype pollution in @feathersjs/commons _.merge via JSON-parsed __proto__
The _.merge(target, source) utility exported by @feathersjs/commons recursively merges source into target by iterating Object.keys(source). When source was produced by JSON.parse and contains a proto (or constructor / prototype) key, that key is returned as an own-enumerable property. The recursive merge then resolves target['proto'] to Object.prototype and writes the attacker-supplied properties onto it, polluting the prototype for all plain objects in the process for the lifetime of the Node process. …