Mozilla Firefox 4.0 Beta 6

The Firefox 4 Beta includes the Feedback Add-on which includes you in user studies. No data will be sent to Mozilla without your permission.

Firefox 4 Beta includes Feedback Add-on based on Mozilla Test Pilot

Once you install the Firefox 4 Beta, you will notice the Feedback Add-on in the upper right corner. You can use this to provide instant feedback at any time. You will also be notified about user studies (run by Mozilla Test Pilot) which collect information about how you use Firefox, but not which websites you visit. You have control over your participation, and can choose to opt out of any study, or see what data has been collected. You will be asked before any data is sent to Mozilla. Please seethe Feedback Add-on privacy policy for more information.

Mozilla Firefox Official Web