Loosen the nuts holding the master cylinder to the power booster. If fluid drips out the master cylinder is bad. Replace it ASAP. The master cylinder will totally fail soon and the fluid will eventually spill over into the booster and deteriorate the diaphram. In fact, if there is considerable fluid spilling out it might be worthwhile to buy a “loaded booster” which is a booster and master cylinder assembly often priced at a considerable savings.
Sooner is much cheaper than later.