Many Firefox extensions including the "recommended" ones which are claimed to be actively monitored are breaking Mozilla's extension policies by secretly sending telemetry, injecting advertisements, load and execute external resources, etc.

None of the ones I reported have had their recommended status revoked, several ones have since even been allowed to publish new versions where the same violations are still present and even a few published updates that introduced additional violations.

To Mozilla: If you want to change the world, start with yourself.

To the rest: Whenever you install or update an extension, always go through its published source first. You can get to it by right-clicking the install/download button to "save as" and then simply unpacking the xpi file.