Yellowish-green liquid on top of stopper?

[emress]

I've had my first lager in the fermentation chamber (freezer) for about a week. I've been checking on it regularly and it's been fermenting fine and has a nice krausen on it. There have been fine bubbles of sanitizer building up on top of the airlock, but it has not needed a blow off tube. Today when I checked on it, a layer of yellowish-green liquid was coating the top of the stopper (outside of the carboy). It's fairly thick. I tasted it off of my finger, which was a mistake: very sharp tangy flavor with a hint of beer. I wiped the rest off the stopper (before taking a picture, whoops!). Is this some sort of infection? the airlock is jammed tight inside the stopper, and the beer does not have any strange colors in it, so I'm just flummoxed.

Does anyone know what this is? Is my beer likely ruined?

 

[oogaboogachiefwalkingdeer]

Sounds like hop residue.

 

[emress]

I've decided it must be star san that reacted with something. Not sure what happened, but I'm relieved that my beer isn't ruined!