Steps to reproduce:

1. open a section (section A) for editing
2. wait until the number of the edited section changes (for example a previous section is archived)
3. press save

This will result in the section being saved in the wrong place - the section which has the old number of section A will be overwritten with a copy of A. Example:
http://commons.wikimedia.org/w/index.php?title=Commons:Village_pump&diff=43140492&oldid=43139012

It should result in an edit conflict instead.

Version: unspecified
Severity: minor