Ive been brewing for about 10 months, and this never happen....
The foam from the fermenter has actually come up and is in my airlock. It has since settled, but there is a lot still in the airlock.
Is it ok to leave in there?
I would sanitize some foil. Pull the airlock out and cover the hole with the foil and clean up the air lock and put it back.
is it the krausen?
if it is, get a blow off asap.
if it's just the starsan or whatever you have in there foaming from the C02, thats normal.
I shoved a hose into my airlock and another end into an empty bottle for 2 days and then put up a new airlock and threw the dirty one into a cleaning solutions...