firebase/firebase-js-sdk

Firebase JavaScript SDK utilizes a "FIREBASE_DEFAULTS" cookie to store configuration data, including an "_authTokenSyncURL" field used for session synchronization. If this cookie field is preset via an attacker by any other method, the attacker can manipulate the "_authTokenSyncURL" to point to their own server and it would allow an actor to capture user session data transmitted by the SDK. We recommend upgrading Firebase JS SDK at least to 10.9.0.

This affects the package @firebase/util before 0.3.4. This vulnerability relates to the deepExtend function within the DeepCopy.ts file. Depending on if user input is provided, an attacker can overwrite and pollute the object prototype of a program.