It might be spillage from when it was filled - but you cannot take that risk.
Check the brake line all the way up from the banjo union at the top of the caliper to the reservoir - see if there is any evidence of fluid on the outside of the hose all the way up to the master cylinder on the handlebar.
Then check all of the metal unions - there's only one set on the front right fork leg. Make sure it is the one connected to the front brake caliper hose. It is the upper bracket on the right fork. So there is one hose conencted from the bottom, one hose connected going up, and one pipe heading across the mudguard - the front one.
Then clean up each joint. Make sure that they are dry.
Squeeze the brake lever hard a few times. Really hard.
Then go back to each of those joints with a clean paper towel (coloured if you have it) and wipe around the joints and check for anything that is now wet.
The do a similar thing with the rear brake circuit. The lower hose from the front left caliper goes to a metal union which is behind and lower than the one for the front brake. A hose comes from up behind the steering head. A pipe heads across the mudguard (the rear metal hose) to the front left caliper centre piston. Check those joints. int he same way, clean and dry and then pump the rear brake pedal hard a few times. Go back and check for leakage.
The metal pipes across the mudguard are joind to the metal union 'block' with a compression fitting. Check that is not leaking where the pipe emerges from the gland nut and is not leaking near the threads. Best seen with a bright light from the other side of the wheel.
If you cannot find anything, then it may be an idea to leave the front leer held back overnight and the brake pedal pressed down and check again in the morning.
The alternative is a spill when fluid was last replaced - or perhaps the brake pads were repalced without opening the master reservoir ont he handlebars.
Wrap absorbent cloth around the reservoir. Turn handlebars fully to the left and turn the ignition key to lock the steering. Unfasten the two screws for the cover and carefully remove the metal cap, the white insert that keeps the diaphragm in position, along with the diaphragm.
The level should be at the line that is part of the casting on the inside of the reservoir. If your brake pads have been in a while, the pads will have worn down and the fluid will be correspondingly lower. If the fluid is topped up part way through the life of the pads then when the pads are replaced, the pistons need to be pushed in and the fluid returns to the reservoir, but there is now not enough room for it. It may be under pressure in there and has leaked out as a result.
Check things out, let us know what you find.
In the diagram below, I have coloured the lines fromt he front brake lever in light blue.
The lines from the brake pedal are pink
looks more like a fork seal.
