Chainsaw Repair

Some of them do that. It's a common issue. Check to see if it's leaking out the oil hole and not somewhere else. Some people find it helpful to loosen the oil cap off and then tighten it up when you're done using it to relieve any pressure in the tank.
You should also check the two rubber pieces that are the pick up into the tank, and the outer seal half to make sure they're in good shape. I think \I've heard that the pick up piece cracks sometimes.