(From https://bugzilla.mozilla.org/show_bug.cgi?id=1694684)

Summary:
There is an open redirection vulnerability in the path of:

https://pollbot.services.mozilla.com/

Description:
An attacker can redirect anyone to malicious sites.

Steps To Reproduce:
Type in this URL:

https://pollbot.services.mozilla.com//evil.com/
As, you can see it redirects to that website when you inject this payload:

//evil.com/
evil.com was used as an example but this could be any website note, the // is the bypass.

Supporting Material/References:
https://cheatsheetseries.owasp.org/cheatsheets/Unvalidated_Redirects_and_Forwards_Cheat_Sheet.html

Impact

Attackers can serve malicious websites that steal passwords or download ransomware to their victims machine due to a redirect and there are a heap of other attack vectors.