What it looks like if you close MediaViewer. Yes, I uploaded a screenshot of a black tab.
- Go to https://wikimediafoundation.org/wiki/Template:Staff_and_contractors#Fundraising_Operations
- Click on the picture for "Juli Matthews of Swagbot". MediaViewer is loaded.
- Click the X to close MediaViewer.
Expected result: MediaViewer closes.
Obtained result: That tab is now a completely black screen, and it cannot be dismissed.