Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability in Mozilla Convict. This allows an attacker to inject attributes that are used in other components, or to override existing attributes with ones that have incompatible type, which may lead to a crash. The main use case of Convict is for handling server-side configurations written by the admins owning the servers, and not random users. So it's unlikely that an admin would deliberately sabotage their own server. Still, a situation can happen where an admin not knowledgeable about JavaScript could be tricked by an attacker into writing the malicious JavaScript code into some config files. This issue affects Convict: before 6.2.4.

This affects the package convict before 6.2.3. This is a bypass of [CVE-2022-22143](https://security.snyk.io/vuln/SNYK-JS-CONVICT-2340604). The [fix](https://github.com/mozilla/node-convict/commit/3b86be087d8f14681a9c889d45da7fe3ad9cd880) introduced, relies on the startsWith method and does not prevent the vulnerability: before splitting the path, it checks if it starts with __proto__ or this.constructor.prototype. To bypass this check it's possible to prepend the dangerous paths with any string value followed by a dot, like for example foo.__proto__ or foo.this.constructor.prototype.

The package convict before 6.2.2 are vulnerable to Prototype Pollution via the convict function due to missing validation of parentKey. **Note:** This vulnerability derives from an incomplete fix of another [vulnerability](https://security.snyk.io/vuln/SNYK-JS-CONVICT-1062508)