How it was found

Description

A user can change their name to a URL in order to send email invitations containing malicious hyperlinks.

Steps to Reproduce

1. Create a new Instacart account with the first name http://example.com
2. Navigate to https://www.instacart.com/store/referrals
3. Send an email invitation to an email address that you control

You will receive a new email with the first word being a link to a potentially malicious site.

Consequences

This permits users to send malicious/phishing links to potential clients. It could also have an effect on how spam filters treat instacart.com emails.