Which blocklist are you looking for? For example:

• bad add-ons
• Tracking Protection
• phishing/malware
• something else

I actually don't know where you could download those in an easily readable format, but the data used by Firefox is stored in various folders on your computer.

You can find the current blocklist as blocklist.xml in the profile folder.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

See also:

• https://blocked.cdn.mozilla.net/