To report a security issue, please use http://g.co/vulnz. We use http://g.co/vulnz for our intake, and do coordination and disclosure here on GitHub (including using GitHub Security Advisory). The Google Security Team will respond within 5 working days of your report on g.co/vulnz.
Select the I want to report a technical security or an abuse risk related bug in a Google product (SQLi, XSS, etc.) option and complete the form.