What model is it? There are a few home owner grade Stihls notorious for this.
Did you run it recently & have you cleaned out the oil holes & channel in bar?
Like others said, a little dripping out of the oiler hole is normal. I have 3 that do it. If its leaking out of the case, thats not good. A bad seal there, could overheat your saw quick. You can do a vacume test on it to determine a leak.
Arboursite.com has alot of saw gurus. You could ask there too.