Using "Post names" as Permalinks can lead to same url for a post and page.

[Da9L]

To reproduce the error:
Use permalinks as "post name" meaning that the name of the post or page is used as identification for the url..

Create a page named news.. this will, with the above settings make a permalink looking like this: ​http://www.siteurl.com/news/

Then afterwards go make a post also named news.. This creates the same permalink (​http://www.siteurl.com/news/), resulting in wierd behavior as you can imagine..

I believe this is a bug, since not so skilled users will be very confused as to what happens.

[jeremyfelt]

Thanks for the report, @Da9L. This is a duplicate of #13459.