See the following article.

• Cannot remove an add-on (extension or theme)

Also see other questions about this topic.

• https://support.mozilla.org/search?q=sweetpacks

Sweetpacks is adware, and should be uninstalled from control panel first. This will likely to remove it from browser aswell. Anti-Malware programs detect Sweetpacks, so you can run Adwcleaner or Junkware removal tool scan.

This worked great. Used the uninstaller in CCleaner and removed the SweetPacks Updater. Restarted Firefox and no add.on.

MalewareBytes did not initially detect SweetPacks when I did a flash scan. Will do a complete scan just to be safe.

Thanks

Look for SweetPacks updater or SoftwareUpdater and uninstall it.

http://deletemalware.blogspot.com/2013/04/how-to-remove-start-sweetpacks-and.html

Then run Malwarebytes and AdwCleaner. If it's still there, reset Firefox.