Q: Who can be affected by this issue? A: Anyone. Q: Why is this a problem? A: This can be abused to redirect users to any harmful website.
Attacker could redirect any Victim to a desired malicious website / banned website like (evilzone.org).
Open Facebook with Google Chrome or Chrome for Android.
Go to https://m.facebook.com/messagingconfirmation?action_url=https://evilzone.org .
That's it :)
Windows 10 Google Chrome 87.0.4280.141 (64 bit) P.S: This wont work on Safari or other Browsers.