If grease or oil as most grease types can "melt" from heat or age.
Upper or lower ball joint have Rubber boots to seal.
Likely one or both failed and grease leaked.
Boot can fail from old age, too much grease "popping" them, etc.
Boot fail won't kill you. Clean up up the grease mess and check for play in the ball joint. Play there = dead BJ. No play then can drive for a while and replace when more time/money.
Wheel Bearing Grease leak can F'd the brake parts. look for grease on dirt shield, back rotor, caliper and pad.
Should be easy to find just removing a wheel.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave