During the last 3 days I participated in giving a workshop about using and creating maps, including how to contribute to OSM. While folks tried to create their OSM accounts, some ran into an issue that I could reproduce. I’m not 100% sure if this is the best place to report this, but hopefully it’s at least not too off-topic (and I didn’t find an existing thread here neither)!
For the actual bug:
When one submits an account creation form at https://www.openstreetmap.org/user/new and it fails to validate (e.g. for the user name being taken or the password being too short), one is redirected to https://www.openstreetmap.org/user - on this page the cloudflare challenge never properly loads - and so account creation submissions will always be rejected for not being human and end up on the /user page again - leading to a constant failure loop.
If one notices this, it’s easy enough to go back to /user/new to try again, but for people not too deep into (web) tech, this is quite confusing behaviour and blocked a good number of our workshop participants from creating accounts, so ideally after a failed form-validation one should end up on a page where one can successfully fix the validation errors instead of being soft-locked 
