Jodit Editor is a WYSIWYG editor with written in pure TypeScript file and image editing capabilities. In versions prior to 4.12.18, Jodit.configure(options) — and the internal ConfigMerge / ConfigProto helpers — merged user-supplied options into the editor configuration without filtering prototype-mutating keys, potentially causing a Prototype Pollution vulnerability. A payload nested under an existing plain-object option such as controls could reach and mutate Object.prototype. Applications that pass user-controlled or partially user-controlled configuration into Jodit.configure() may be vulnerable. This issue was fixed in version 4.12.18.

Affected: npm: jodit

### Summary `Jodit.configure(options)` — and the internal `ConfigMerge` / `ConfigProto` helpers — merged user-supplied options into the editor configuration without filtering prototype-mutating keys. A payload nested under an existing plain-object option such as `controls` could reach and mutate `Object.prototype` (prototype pollution).

### Affected - Package: `jodit` (npm) - Versions: `< 4.12.18` - Public API: `Jodit.configure(options)`

### Proof of Concept ```js import { Jodit } from 'jodit'; delete Object.prototype.polluted; Jodit.configure(JSON.parse('{"controls":{"__proto__":{"polluted":"yes"}}}')); console.log(({}).polluted); // "yes" (before the fix) delete Object.prototype.polluted; ```

### Impact Applications that pass user-controlled or partially user-controlled configuration into `Jodit.configure()` could be vulnerable to prototype pollution: unexpected property injection, logic bypass, denial of service, or secondary security issues.

### Patch Fixed in 4.12.18 by rejecting `__proto__`, `constructor`, and `prototype` at every merge level in `ConfigMerge` and `ConfigProto`.

### Credit Responsibly reported by Junming Wu.