How to fix a leaking differential on a BMW?

I recently noticed that my BMW has a leaking differential. What could be causing this and how can I fix it? Any advice on what parts I may need to replace or how to properly troubleshoot the issue would be greatly appreciated.

First of all, you should locate the source of the leak. It could be a damaged seal or gasket, a crack in the casing, or a loose plug or bolt. Once you have identified the source, you may need to replace the damaged parts or tighten the loose bolts to stop the leak.