Pitts brake fluid

While recently doing some extended inverted time, practicing rolling out on
headings while still trying to maintain altitude, I noted some brake fluid
had leaked onto the pedals and got rather slippery. I hadn't noticed this
before, as most of my stuff so far has been positive Gs. I'm assuming the
fluid is leaking out the vent holes. Has anyone had this happen before, or
do I need to look further at my brake system? Suggestions?

Thanks,

al MacDonald