When viewing the list of installed plugins, it's possible to click on a plugins name. This will open a popover with the plugin details. Due to incorrect CSP headers, this popover currently fails to load any screenshots.
Any reason you chose not to add a UI test to avoid this in future?
I'm not sure if we want to test pages loading external images from our servers in the UI tests. This can easily cause random failures if our server doesn't respond in time and it also causes traffic we can avoid.