It looks like you are able to hover over the border of the filter buttons below the drop downs. See video below since that's hard to understand from my poor description (inspector tool at the end shows the offending borders). It seems to happen in both chrome and firefox (no extensions). 

You must be running some kind of extension because DDB doesn’t have a darkmode.

Quote from IamSposta >>

You must be running some kind of extension because DDB doesn’t have a darkmode.

 
Put a sunglasses (🕶) emoji in the encounter builder search field it's an easter egg that dndbeyond has had there for a long time (like the party wizard). Also if you watched the video you'll see the original light mode. I primarily showed the easter egg dark mode because the bug is easier to see but it still occurs in both.

Quote from Jay_Lane >>

Quote from IamSposta >>

You must be running some kind of extension because DDB doesn’t have a darkmode.

 
Put a sunglasses (🕶) emoji in the encounter builder search field it's an easter egg that dndbeyond has had there for a long time (like the party wizard). Also if you watched the video you'll see the original light mode. I primarily showed the easter egg dark mode because the bug is easier to see but it still occurs in both.

 Nice. Good catch.