There is a hidden gold assignment tucked away in Battlefield 4. It's called "Phantom Prospect" and it involves quite a bit of work to actually earn once you've unlocked it.

First thing's first, however, let's find out how to unlock it in the first place!
  • This cannot be done in Firefox for some reason. Any other browser seems to work fine.
  • You must have Battlefield 4 Premium.

Steps to unlock:
  1. Go to Battlelog
  2. Click on Leaderboards
  3. Scroll to the bottom of the Leaderboards page
  4. At the bottom left of the page is a small, faded skull icon (See Screenshot)
  5. Click on the skull icon
  6. When the dialogue prompts you for a password enter "bumpinthenight" (without quotes)
  7. Congratulations, you've unlocked a new gold assignment called "Phantom Prospect"