A prototype pollution vulnerability exists in Ember.js prior to 3.24.7, 3.28.10, 4.4.4, 4.8.1, and 4.9.0-beta.3. An attacker can set paths like __proto__.__proto__.isAdmin to mutate unexpected objects, including Javascript intrinsics like the global Object. Depending on the specifics of your application, this can be leveraged as part of an attack to steal user credentials.