I was using the Visual Editor to update the article
I made some changes but then realised that the changes involved the wrong URL so I backed up of the edit by clicking Article. It asked the Leave/Stay question and I said Leave.
So I tracked down the right URL and then source-edited the article in source mode (no particular reason for choice of source mode, just did, I am fluent in both). I made the changes I wanted to and Saved. I then went into Visual Editor again and it seemed like the changes I had saved hadn't been. I went back, looked at the History, and the versions there and everything seemed OK. I started the VE again, same thing, I was seeing the aborted edit. Then I noticed up in the top right the little box that said "Changes recovered: Your unsaved changes have been automatically recovered." Nothing I could do would open the current version of the file in VE (I logged out and I logged in again, I made a trvial changes using the source editor.). So I tried to see what happened if I saved those abandoned changes, and yep, it saved them, over the top of subsequent edits.
So there appear to be two big problems here.
1. I cannot abort a VE edit! because if I do, I can never use the VE again on that article untiI publish it!
2. Publishing the abandoned edit does overrides all subsequent edits without creating an edit conflict.
The capacity to do damage here is incredible. How many minutes/hours/days/weeks later might the VE user restart an aborted edit and unintentionally overwrite all subsequent edits? How many times has it already happened? I noticed because the article was quite small and there was lots of whitespace around my aborted edit, but if the changes had occurred inside a more "text-heavy" area, then I may not have noticed it.
This is the version of the article when I opened it in VE, started making changes, realised the URL was wrong, then aborted it:
This is the version of the article I created with my subsequent source edit (fixing the URL and presenting it as a cite web}}
This is the version I then opened in VE and got the "Changes recovered". I aborted the VE edit . I reattempted opening in VE a few times, same problem, aborted each time.
This is the version of me doing another source edit (just for testing purposes, added a space).
Again I re-entered VE and got the "Changes recovered". Now thinking, if I save this, will it stop me or give me an edit conflict. So I saved it. The VE happily saved it and there was no edit conflict. And yes I had just overwritten my previous two source edits.
I then used "undo" to roll it back to a good version.
I can now open the article in VE without the "Changes recovered".
I think this new feature needs to be turned off until it has been fixed in two important ways:
1. it will not operate in "edit conflict" situation (i.e. where the aborted edit does not apply to the last version of the article)
2. even if the aborted edit does apply to the last version of the article, the user must be allowed to click something to say "no, I don't want my changes recovered -- I aborted for a very good reason, it was no accident".