Bug in importing the data feed into google merchant center

HI there,
I am reporting a potential bug that I encountered in the integration with Google Merchant Center:

This is the website of the shop:
Cartolibreria Biondi

This is the feed of the products
http://cartolibreriabiondi.com/?rss=true&action=product_list&xmlformat=google

If I try to add the data feed into google Merchant i obtain the following error:
“These characters are not allowed: &, /, :, =, ?”

https://wordpress.org/plugins/wp-e-commerce/