This variant of a phishing attack uses unicode to register domains that look identical to real domains. These fake domains can be used in phishing attacks to fool users into signing into a fake website, thereby handing over their login credentials to an attacker.
This affects the current version of Chrome browser, which is version 57.0.2987 and the current version of Firefox, which is version 52.0.2. This does not affect Internet Explorer or Safari browsers.
How to fix this in Firefox:
In your firefox location bar, type ‘about:config’ without quotes.
Do a search for ‘punycode’ without quotes.
You should see a parameter titled: network.IDN_show_punycode
Change the value from false to true.
https://www.wordfence.com/blog/2017/04/chrome-firefox-unicode-phishing/