Say you want to post on an imageboard anonymously. Well, I did that and while it worked, however it says "required permissions not granted, reverting to the system file picker" when I browsed my photos on there. What does this mean? Does it mean that people (such as the website owner) gain access to my camera roll that way? Also, are there any exploits on Tor that target this?
That is nothing to worry about. That message appears if you try to upload a file but the browser does not have permission to access the camera or microphone. Instead it will only allow you to upload existing files through the default file picker. The website owner does not get access to your camera roll.
For more details see: https://bugzilla.mozilla.org/show_bug.cgi?id=1538270