2001 sable/taurus trans leak

I have a 2001 sable and it recently started leaking small amounts of transmission fluid on the driveway. Today i checked the fluid, which was still in the normal range, and while I had the engine at idle I noticed a small plug like an oil pan plug, except miniature on top of the trans and from around that plug came the small amounts of trans fluid, so i found the source of the leak, but don't know the purpose of this plug and if i should be tightening it. Any info is appreciated. Thanks