In short: Pingsender is a separate process that Firefox spawns on shut down to send telemetry data to Mozilla.Similar telemetry collection from operating systems like Windows 10 caused a lot of ruckus, so if you want to disable pingsender.exe for privacy reasons, you can find further instructions over here.
Firefox users may load about:telemetry in the browser's address bar to check the data that Mozilla is collecting.
Those who don't want to provide Mozilla with data can turn the data off under about: preferences#privacy.
Firefox uses pingsender.exe to collect telemetry data
Posted on Tuesday, October 17 2017 @ 11:27 CEST by Thomas De Maesschalck