For example:
https://www.mediawiki.org/w/index.php?title=Project:Sandbox&action=edit
Title: Editing Project:Sandbox
https://www.mediawiki.org/w/index.php?title=Project:Sandbox&veaction=edit
Title: Editing Sandbox
The latter should be the same as the first one.
Also happen in:
https://www.mediawiki.org/w/index.php?title=User:Example&action=edit
https://www.mediawiki.org/wiki/User:Example?veaction=edit