The legacy version of LeechBlock included an option to hide the LeechBlock extension in Firefox’s Add-ons Manager, preventing users from easily disabling or uninstalling it. It’s no longer possible to provide this option due to restrictions on extensions that were introduced in Firefox 57.

However, there is another way to hide LeechBlock in the Add-ons Manager. Carefully follow these steps:

• Locate your Firefox profile folder.
• Create a new folder chrome inside your profile folder (if it doesn’t already exist).
• Create a new file userContent.css inside that folder with the following content: [addon-id='leechblockng@proginosko.com'] { display: none !important; }

You will need to close all Firefox windows and restart Firefox for it to take effect.

Note: If you’re using Firefox 69 or above, you’ll also need to go to about:config and ensure the toolkit.legacyUserProfileCustomizations.stylesheets preference is set to true (go here for more detailed instructions).