Tested this in a 7.8 created project. I don't have issues with blue boxes.
It looks like this:
So I guess that its part of the theme file part of the 7.6 release.
If you still use the default theme, then I suggest that you create a new project in 7.9 and copy paste the theme files of the new project to your current project.
Or maybe download the Atlas UI resources module, it seems that this contains the upgraded Atlas UI framework