URL: https://www.wattpad.com/

Browser / Version: Firefox Preview Nightly 200601 (🦎 78.0a1-20200529095426)
Operating System: OnePlus6 (Android 10) 1080 x 2280 pixels (~402 ppi pixel density)
Tested Another Browser: Yes Chrome

Problem type: Something else
Description: The "Sign up with Facebook" button is broken
Steps to Reproduce:

1. Access https://www.wattpad.com/
2. Observe the "Sign up with Facebook" button.

Expected Behavior:
The button's label must be correctly displayed and the button is functional.

Actual Behavior:
There are additional letters and symbols next to the button's label and the button is not functional. An error message is displayed upon tapping the button.

Notes:

1. The issue is not reproducible on Chrome Mobile 83.0.4103.83
2. Screenshots attached.

Watchers:
@softvision-oana-arbuzov

This is how the page looks on Firefox Preview Nightly:

And this is the page on Chrome:

From webcompat.com with ❤️