That researcher was Ian Carroll, who created a new "Stripe, Inc" company in Kentucky, a clone of the one registered in Delaware, and was therefore able to get an EV certificate issued for his new company that looked very similar to one issued for the Delaware company.

His original research site appears to no longer be online (https://stripe.ian.sh/), but you can read more about it in these articles:

https://www.bleepingcomputer.com/news/security/extended-vali...

https://arstechnica.com/information-technology/2017/12/nope-...