Today, I ran maintenance/update.php on an installation. Now, when certain pages are invoked with "Edit," an entirely different page is invoked -- it is almost as if an index in the database were skewed. It is now possible to save the page and stomp over whatever was there before. Has this been observed before? I'm not even sure how to debug this -- suggestions will be appreciated!
Here is some version identification.
MediaWiki: 5a3173d06b605a8c86ace08efc9e9c290f7f171a VisualEditor: b6ad119f153cdd0f88e3152c5961785c3d46e72a