<ul data-eligibleForWebStory="true">Machine Unlearning (MU) is used to update machine learning models efficiently by removing training samples without retraining from scratch.MU is employed to provide privacy protection and regulatory compliance but can also increase the model's vulnerability to attacks.Existing privacy attacks on MU require access to both the unlearned model and the original model, limiting their practicality in real-life scenarios.A novel privacy attack named Apollo is proposed, focusing on label-only membership inference towards MU.Apollo operates under a strict threat model where the adversary only has access to the label outputs of the unlearned model.The attack aims to determine if a data sample has been unlearned and shows high precision in identifying unlearned samples.