My CSS has been leaking around my oil filter for quite a while (I have the L&N filter adapter w/ spin on filter). So I tightened the filter a bit more. Still dripping off the bottom of the filter. So I take the filter off and tighten the adapter. Still dripping. By now, the area around the filter is dirty, so common practice is to clean the area and see where it's coming from. Once I've done that, it appears the leak is coming from the adapter to the engine. So I pull the adapter off and found the problem: there's a rubber o-ring around the adapter (like the rubber ring you put on your factory filter canister) and by now it's pretty flat. I call L&N and the tech supt guy tells me they've just started selling an o-ring kit for the adapter. I order it up - $21.
I checked my records and my adapter is 5 yrs old and 40K mi. So for those of you who have the adapter, be aware it can start to leak due to a flat o-ring. Here's the link:
https://lnengineering.com/spin-on-filter-adapter-o-ring-kit.html