Strange accounts with names like "ios_....................."

In the latest Greek 27300 Coin Challenge, there are now three participants with this kind of weird screen name. Are these test accounts? Results of a bug or hack?
The challenge board:

They are in the 90 Day Korean Challenge as well.

It’s not a bug, those are unregistered users from the LingQ iOS app. We now allow them to use the app and check it’s functionality even before they register. That’s why they get random temporary usernames you mentioned.

Good to know, thank you :slight_smile: