Not uncommon at all
Check:
The Rocker Cover gasket all round....it could be dribbling down from above
the tighness of the oil line coming into the top of the filter....
whether there is oil being pumped out of the Filter housing to block gasket..
whether there is oil being pumped out of the electrical sender on the top right of the Filter housing.....these are notorious leakers...
But First

..brush the entire area witha Hydrocarbon based degreaser (glendale make red stuff) rather than the caustic soda based ones...then carefully hose off....and make sure the entire area is clean...
drive it round the block (not far!!)...thebn see where the oil is coming from...Guuuudddd Leeerrrkkk
