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Code reviewHardcr-g570
Subject Prototype pollution vulnerabilityLevel Senior–Staff~28 minCommon in Security interviewsIndustries Software development

Question

Review this JavaScript deep-merge used on request bodies (Node.js).

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Code to reviewjs
function deepMerge(target, source) {  for (const key in source) {    if (typeof source[key] === 'object' && source[key] !== null) {      if (!target[key]) target[key] = {};      deepMerge(target[key], source[key]);    } else {      target[key] = source[key];    }  }  return target;} app.patch('/settings', (req, res) => {  const settings = deepMerge(loadDefaults(), req.body);  saveSettings(req.user.id, settings);  res.json(settings);});
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