I did a little more testing and I found a bug. If the image has no alt or title attributes and the pinterest button is clicked the description reads ‘undefined’.
Best,
Tom
This is a duplicate question of http://ww.wp.xz.cn/support/topic/image-discription-1. Sorry. Marking it as resolved.
I think I must have been doing something else wrong because now it’s working. Sorry for the inconvenience.
