You can use many online photo censor in google like this or this. i believe there are so many other apps to do something like that. if you don't want to use that, you can try using brushes+eyedropper in paint or paint 3D. pick the background color with eyedropper and brush sensitive info with that color
You can use some apps like GIMP or Paint.net or other photo manipulation apps you know. you need some basic knowledge about photo editing but i'll try to help you. I'll give you some link to the tutorial if you don't know how to blur image with that apps.