Welcome to Allpar. Any fluids other than brake fluid in the master cylinder can do a lot of damage to the rubber brake parts. Swollen rubber can cause a loss of brakes.
Don't drive the vehicle or pump the brake pedal. You may be able to bleed the contaminated fluid out of the master cylinder before it reaches the wheels.
You will need a helper and hopefully someone who is familiar with bleeding brakes.
You may wind up having to replace the master cylinder for safety, then bleed and flush all four wheel brakes with fresh DOT 3 brake fluid.
Best of luck to you.