When you read a blog post with chrome, there's an issue where a square box.
It is said that a square box can be seen if there is an extension related to the pop-up or a pop-up during the chrome extension plug-in.
In my case, the issue occurred due to "Google translation" plug-in.
Therefore, the issue is solved by shutting down the plug-in or using other Internet Explorers (explorer, edge, safari, etc.).