The obvious way is usually enough: check through the addon’s settings to see if there’s an option to disable it. Eg, under Ghostery’s hamburger-menu is a ‘Support Ghostery’ setting section, with three different boxes for enabling or disabling phone-home behaviour. Besides that, you can glance at the user reviews on the Mozilla add-on download page, on Reddit, the top few Google results, and so on. It also helps to be careful about where you look for privacy addon suggestions in the first place.
How do you know whether an extension such as Adblock Plus or uBlock phones back?
The obvious way is usually enough: check through the addon’s settings to see if there’s an option to disable it. Eg, under Ghostery’s hamburger-menu is a ‘Support Ghostery’ setting section, with three different boxes for enabling or disabling phone-home behaviour. Besides that, you can glance at the user reviews on the Mozilla add-on download page, on Reddit, the top few Google results, and so on. It also helps to be careful about where you look for privacy addon suggestions in the first place.