A report released by security experts from Sucuri and Unmask Parasites says Google has started using a new combination of factors when blacklisting sites. Google appears to be using HTTPS status for Safe Browsing alerts. Google has been pushing for wider HTTPS adoption in Chrome, and not just Chrome. Most of these cases happened with relatively new sites that hadn’t had the chance to build a reputation, experts say. Google was seeing newly registered domains being used to collect password and credit card data via HTTP, and thought they were used for phishing.
Source: https://www.bleepingcomputer.com/news/security/report-reveals-google-is-blacklisting-some-sites-that-handle-passwords-via-http/