Security vulnerabilities: Prototype Pollution and ReDoS.

In Simple Words:

• Prototype Pollution: Merging untrusted user objects directly into existing objects mutating __proto__. Fix: Use Object.create(null) or validate inputs with Zod.
• ReDoS (Regular Expression Denial of Service): Evil regexes with catastrophic backtracking freeze the Event Loop. Fix: Avoid nested quantifiers and use safe regex engines like re2.

// Prototype pollution vulnerability:
// target["__proto__"]["isAdmin"] = true;

// Safe object creation:
const safeDictionary = Object.create(null);
safeDictionary['user_input'] = 'value'; // Cannot pollute Object.prototype!