1999 mule 2510 Brake leak
 

hi all, I'm new to this forum. I let my neighbor use my mule yesterday to take his son out for his birthday he was driving mainly on trails and did not dog it out. however he was driving around all day with the parking brake engaged. upon unloading the mule off the trailer we noticed some brake fluid leaking from the drivers side rear drum. is this normal where should I start.