Works perfectly, even under 8.5.2. The support is super fast. I highly recommend the extension and the developer !!!
Version 8.0 Ready!
A sleek, modern, responsive solution for Image PopUps on your Concrete5 5.7x website. With Image Popup you can select an image from your C5 File Manger to PopUp as a full screen overlay.
Popups can be activated by Thumbnail Image, Text Link, On Page Load or from a CSS Selector anywhere on a page. File Sets of images can be selected to display as a gallery.
Demo and Documentation at: http://webli.us/add-ons/pop-utilities/image-popup
See all our PopUp utilities at http://webli.us/add-ons/pop-utilities
Visit Webli's Concrete5 CheatSheet