Toilet Leaking

Hi all would normally search first but phone is dying and bathroom floor is soaked. Water is dripping at a brisk pace from the brass fitting on the bottom of the toilet flush handle. Has anyone experienced this before? I would post a picture but can from phone.

The metal fitting is round and flat on bottom with nothing coming out of the bottom. I have turned the water off and will investigate further in the AM.

Thanks for any help

Chip