"Checking your browser" hangs due to user agent, prevents sign in

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

Summary

The sign in doesn't work when using GNU IceCat (while it works in Chromium).

Steps to reproduce

Install GNU IceCat, such as available from GNU Guix (guix install icecat), navigate to gitlab.com and attempt to sign in.

Other possible ways to reproduce

1. Use a Firefox ESR user agent.
2. Set network.http.referer.trimmingPolicy and network.http.referer.XOriginPolicy to 2
3. DNS over HTTPS setting in browser

What is the current bug behavior?

The sign in process hangs on the Checking your browser before accessing gitlab.com. dialog. Looking at the Network devtools tab in IceCat, I see that a 503 error is returned for the https://gitlab.com/users/sign_in?redirect_to_referer=yes endpoint.

What is the expected correct behavior?

The sign in should proceed normally.

Output of checks

This bug happens on GitLab.com

Possible fixes

Use a less broken anti-DDoS solution provider than CloudFare?