Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isnt sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.
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.