One of my Windows 10 computers that's running Firefox 57.0.4 has recently enabled a 'Widevine Content Decryption Module' plugin from Google. I did not install this and I cannot find a way to uninstall or delete it, but I did 'disable' it. I have three questions:

Widevine is a proprietary digital rights management (DRM) technology from Google used by the Google Chrome and Firefox web browsers (and some derivatives), Android MediaDRM, Android TV, and other consumer electronics devices.Widevine technology supports various encryption schemes and hardware security to restrict consumer access to distributed video content according to rules defined. Update the Widevine content decryption module. First of all, you should try to update the add-on. Widevine provides a market-leading platform for delivering protected premium content at the highest possible quality and is studio-approved for 4K, UHD, HDR and more.

1. How can Firefox (without my knowledge or consent) download, install, and enable this, or any other plugin?
2. How can I permanently delete this plugin from my computer?
3. How can I prevent Firefox from downloading, installing, and enabling other plugins or extensions without my knowledge and consent?

Firefox Widevine Plugin

Widevine Firefox Android

Widevine Firefox Arm

Thank you for your help.