https://addons.mozilla.org/en-US/firefox/addon/9825/
I'm not quite sure how or why it works,but occasionally it seems that when endless pages is on,the edit button will actually seek the next page that was turned on,rather then the page you hit edit on.
Fastest Fox's endless page basically loads the next page whenever it reaches the bottom of a page,so i assume that edit is looking for the last page loaded,even if it was loaded by accident (smaller pictures that autoload the next page tend to see this bug more)
The bugs results are basically that if you accidentally save the changes,the source and tags can be altered to the picture just below that one (unless you immediately notice the tags pulled aren't the ones used by the page)
Just felt i should warn people...that said
Anyone wanna check this picture to make sure the tags are correct? I kind of had the bug here before i decided to turn off the feature :/
Updated by Smashu