Today I had a problem with firefox using too much CPU ressources. I restarted my browser in safe mode to see if any addons were the cause. I also disabled all plugins. After I found the faulty addon, I restartet firefox in normal mode. Unfortunately there is no way to enable any plugins now.
Whenever I enable a plugin it shows as enabled in the plugin list. But plugins are not loaded on sites requireing them (Mozilla's plugincheck doesn't find any enabled plugins either: https://www.mozilla.org/de/plugincheck/).
Restarting the browser doesn't help either. After every restart, all plugins are shown as disabled again.