So it can delete cookies when clicking that new button. It probably does not need history permissions; I will check that.

New feature "Del Browsing Data" ... look above the "About" link when you open the main options page. it probably does not need history permissions because it does not delete history, but it does need cookie permissions. i will fix the history permission shortly.

Won't work on Android until Firefox supports its proxyAPI for Android. I'll update the description of this addon with that info.