Maker.js is a 2D vector line drawing and shape modeling for CNC and laser cutters. In versions up to and including 0.19.1, the `makerjs.extendObject` function copies properties from source objects without proper validation, potentially exposing applications to security risks. The function lacks `hasOwnProperty()` checks and does not filter dangerous keys, allowing inherited properties and potentially malicious properties to be copied to target objects. A patch is available in commit 85e0f12bd868974b891601a141974f929dec36b8, which is expected to be part of version 0.19.2.

Affected: npm: makerjs

### Summary The `makerjs.extendObject` function copies properties from source objects without proper validation, potentially exposing applications to security risks. The function lacks `hasOwnProperty()` checks and does not filter dangerous keys, allowing inherited properties and potentially malicious properties to be copied to target objects.

### Details The `extendObject` function iterates over source object properties using a `for...in` loop without: 1. Checking `hasOwnProperty()` to exclude inherited properties 2. Filtering dangerous keys (`__proto__`, `constructor`, `prototype`) 3. Validating property sources

### Affected Code

**File**: https://github.com/microsoft/maker.js/blob/98cffa82a372ff942194c925a12a311253587167/packages/maker.js/src/core/maker.ts#L232-L241

### PoC ```javascript const makerjs = require('makerjs');

const source = { __proto__: { name: 'Ravi', isAdmin: true } }; const target = { name: 'user' }; const result = makerjs.extendObject(target, source);

console.log(result.name); // Ravi console.log(result.isAdmin); // true ```

### Impact ### Security Implications

1. **Unexpected Behavior**: Properties may appear on target objects but not be own properties, breaking `hasOwnProperty()` assumptions in security-sensitive code.

2. **Security Bypass Risk**: Code relying on `hasOwnProperty()` for validation could be bypassed.

3. **Future Risk**: Lack of dangerous key filtering (`__proto__`, `constructor`, `prototype`) exposes potential attack vect…