Here's a fun bug that was reported by Jens K earlier today: if a user does not have permission to edit images, but they attempt to sort images, that will cause an error that would result in an image being removed completely if they had that permission.
It's a bit of an odd permission set up perhaps, but it makes more sense with something we've added in the upcoming 1.6 which Jens was testing.
Needless to say, that's now fixed and no more images will be removed in v1.5.9. The offending code was added in 1.5.8.
Alongside the fix for removing images, sorting images has been disabled in 1.5.9 when the user does not have the image_edit permission. We'll probably add a new permission in 1.6 or 1.7 which brings back the ability to sort separately from having access to the edit screen.
++ MoreGallery 1.5.9-pl
++ Released on 2017-03-29
- No longer removes images when sort fails (for example because of permissions or a db error) [S11532]
- Disable sort if the user does not have image_edit permission