Why is the rinse aid dispenser leaking in my kenmore elite dishwasher?
Check the cap for damage. Also check the seal around the top of the cap. If the cap is damaged, replacing it should fix your problem.
If you find no problem with the cap, then the dispenser assembly will need to be replaced to fix this problem unless you have a water softener and can do without the rinse aid.
If you need to replace the dispenser assembly, follow the steps in this link of a previous answer to complete this repair:
How do I install the soap dispenser on my Kenmore dishwasher?