did you try closing your browser?
You have 2 variant windows/tabs open

Yes, I did. I also deleted all of the browsing data (cookies, caches, etc.) and restarted my computer. Still not working, the warning is still there.

You may want to file a bug report. Not through the main forums, they don't seem very responsive there, do it through the FAQ or Help pages.

Filling a bug report is probably a good idea. I have just filled in the report. I would inform here if they reply and/or fix the bug!
Dear all,
In my chess variant page, there is a warning 'You have 2 variant windows/tabs open" as shown in the picture below. I have tried everything I could to resolve this issue but any attempts were unsuccessful. I have tried to log out from all of my devices, and also changed the password. Is this a bug? Please help!
Thank you!