parse is a package designed to parse JavaScript SDK. A Prototype Pollution vulnerability in the SingleInstanceStateController.initializeState function of parse version 5.3.0 and before allows attackers to inject properties on Object.prototype via supplying a crafted payload, causing denial of service (DoS) as the minimum consequence.
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.