What would cause brake master cylinder to almost be almost empty?

What is your question?

98 Chevy Lumina V-6. I found the brake master Cylinder almost empty. Filled it up but have seen drops around the back firewall/middle of car some type of fluid recently. Just multiple drops. Some of it trans fluid I think. I don't see any wetness between the master and the booster. I haven't checked the wheel cylinders yet. Is there a brake line that goes from one front brake to the other somewhere between the firewall and engine? Is there any brake fluid blocks, ABS, etc. located around there? Please advise. Thank you.