Hi there!
since one of this last updates the closing-button is still within the markup but not to use and not visible.
(Using Popup Theme Shadow).
Adding the following code in plg_system_jecemediabox/css/jcemediabox.min.css helps out for now:
.wf-mediabox-theme-shadow .wf-mediabox-prev, .wf-mediabox-theme-shadow .wf-mediabox-next, .wf-mediabox-theme-shadow .wf-mediabox-close
{
display: block;
z-index: 1;
float: right;
position: relative;
border: none;
border-radius: 0;
background-color: transparent;
left: auto;
top: 0;
color: #fff;
}
