A new version of Firefox was released on 3/7/17. This is the first version of the browser which has support for classic plugins disabled with the exception of Flash. Plugins like Silverlight and Java will stop working. In Firefox 52, the user can turn on NPAPI plugin support using about:config. Here is how it can be done:
1. Open a new tab in Firefox and enter the following text in the address bar and press Enter or Return on your keyboard: about:config
2. Confirm that you will be careful if a warning message appears for you by selecting I accept the risk.
3. You will then see a long list of preferences in the browser window as shown below.
4. To add a preference, right-click anywhere in the browser window and select New and then the type of preference you wish to add which in this case will be Boolean.
5. Name it plugin.load_flash_only.
6. Select false for the boolean value and click OK.
7. You will now see it show up in your list of preferences.
8. Restart Firefox by closing all open tabs and relaunching it.
Note: With Firefox 53, the ability to restore NPAPI plugin support will be removed completely.