It will only slowly drip out. Wrap a rag around it first and there shouldn't be any mess.
Do yourself a giant favor first and carefully wrap about 4 wraps of a quality PTFE sealant tape (not Harbor Freight) around the threads being careful not to cover the hole in the side of the bleeder. Cut the tape narrower first if you have to.
I have had problems with those whiz bang speed bleeders sucking air past the threads as you release the lever, making bleeding much more difficult than just a regular bleeder that has a solid seal. I wrap all bleeders like that, even vacuum bleeding/flushing can have the same problem.
IMO, those things are OK for a car if you don't have any friends (like me) but no need for those on a motorcycle because you can reach the bleeder and lever by yourself.