Your screenshot shows that you have selected an image (linked/embedded) and applied the White swatch to it.
Could you share the file with us (email@example.com) to take a look?
Adobe InDesign teamMart commented
If anyone is still having this issue. I've had today, upon opening a file for 1st time in 3 days (which at last time of opening was fine) made every white element in my doc black. (as the above problem)
There is a simple fix (at least for me it worked)
Go to indesign / preferences / 'appearance of black' and make sure you select or have selected 'display blacks accurately' from the on screen and print drop downs.
Other things you could do to make sure the system is running graphics correctly are:
Display performance, transparency above or at at-least medium quality.
preserve object level settings is ticked
and you should be fixed.