Nextcloud strange login behavior

Nextcloud version (eg, 20.0.5): 28
Operating system and version (eg, Ubuntu 20.04): Debian 11
Apache or nginx version (eg, Apache 2.4.25): Docker Image
PHP version (eg, 7.4): Docker Image


I use a password manager to manage my passwords. My Nextcloud login data is also stored in this manager.
When I call up my Nextcloud instance, my password manager automatically fills in the two login fields and I then only have to click on “Log in”. That’s how it’s meant to be.

Unfortunately, on the latest version of Nextcloud [Hub 7/V28/newest Docker Image [I use the nextcloud container]] I get an “unknown error” when I try to log in this way. I can find this in the Nextcloud log:

OC\Core\Controller\WebAuthnController::finishAuthentication(): Argument #1 ($data) must be of type string, null given, called in /var/www/html/lib/private/AppFramework/Http/Dispatcher.php on line 230 in file '/var/www/html/core/Controller/WebAuthnController.php' line 89

After some trial and error, I found out that I can bypass the error by loading the Nextcloud login page, letting my password manager fill in the fields and then manually clicking in the email field and then in the password field. If I then click on Sign in everything works. If I don’t click in both fields again before logging in, the error occurs.

I can’t explain this, and even less why it works when I click in the fields before logging in.

How can I fix this?

Are you utilizing Passwordless Authentication? (e.g. Personal settings → Security)

No, very oldschool, email and password

Hmm. Might be this.

Can you check your browser console?

I have just tried again, now I only have the problem on mobile devices, and not always. Just tested it on an iPad. The problem was there again. It is very random. Unfortunately, there is no browser console on mobile devices.

The link would not help me, as I said I do not use webauth but email + password

The link would not help me, as I said I do not use webauth but email + password

You may not be, but you’re still hitting the same area of code for some reason.

What password manager?

I use Bitwarden.