The other day when I popped the hood to let the engine cool i noticed my fluid had overflown. I did have a hard stop but i've had lots of those in the lifetime of the car and never noticed this. Every oil change I suck out some and replace it to keep the fluid fresh, and i never overfill.

 

Your master cylinder should not over flow ~ are you sure you did not over fill? I'd change the cap ~ if thats the orig. cap, I'm sure that rubber seal is tired.