Google Shopping Express is a same-day shopping service ("shop local stores online and get items delivered on the same day") from Google that was launched on a free trial basis in San Francisco and Silicon Valley in spring 2013 and publicly in September that year.
This store XSS was showing at "Shopping Express Checkout" and by adding payload on the parameter "City" in wallet.google.com I could bypass restrictions and trigger this XSS back on Google Checkout.
Image of Proof:
This XSS was trigger just before paying pretty handy don't you think?
Well I report this to Google Security Team and they reply very quick. Fixing this bug within a week:
I'm very happy to be back on Google Hall of Fame and I like to thanks Google Security Team for the reward.
I create a video reproducing this XSS: