Thank you for contacting Mozilla Support about this issue. I appreciate that you are concerned about unauthorized access to your Mozilla account and Sync information.
Mozilla is aware that attackers with access to passwords acquired during other data breaches have used that information to access Mozilla Account and Sync information. We have been able to reset passwords when this has happened in the past but new cases may exist that we do not know about.
If you believe that your account is being accessed without your permission, your first step should be to change your Firefox Accounts password. For more information, please read Change your Mozilla Accounts password and Suspicious activity on my Mozilla account.
- If you have forgotten your Mozilla accounts password, please read I've lost my Firefox Sync account information - What to do.
It's possible that your other online accounts have been compromised. I recommend that you change all of your online passwords (being careful not to repeat passwords for different accounts) and then update any of those passwords that are stored in your Firefox Password Manager. You can read more about how to do that here.
Mozilla is committed to keeping you safe online and is working on new features for Mozilla account to help protect your information.