Water from top vent

The vent that is connected to the top of the kitchen sink. Is it normal for water to come out of it? I know its a vent, but does it function as an overflow too into the kitchen sink? Or is there a blockage causing it to come out the top vent?

Is it Normal for water to discharge from the top vent?
Water comes out and empties into the sink. Is this normal? I thought it was just a vent?

Normally no water should come out the vent. There may be a clog in the drain somewhere.