I was just using my computer normally, not even using the enpass extension, when my fan started spinning up. I opened up htop and saw that an enpass process that seemed to have something to do with firefox seemed to be maxing one of my CPU cores. The htop screenshot can be found here, but a transcript of the process name is "/opt/Enpass/bin/EnpassHelper/EnpassNMHost /home/redrield/.mozilla/native-messaging-hosts/EnpassNMHost.json email@example.com".
What is this process doing? It doesn't seem critical to the app, because it doesn't break anything when I SIGTERM it, but it seems lik