'preview' query var is not removed from post URL if a post has been published

[amit]

If a post has been published, it can be loaded via a URL containing 'p' & 'preview' query vars and a canonical redirect is not done to post permalink which results in two URLs with same content and causes a duplicate content issue with search engines like Google.

For example:

​http://example.dev/?p=731

would redirect to

​http://example.dev/post-slug/

but

​http://example.dev/?p=731&preview=true

does not redirect anywhere & remains same. So if this URL is somehow indexed by search engines they would have two URLs with same content:

​http://example.dev/post-slug/
​http://example.dev/?p=731&preview=true

and thus the duplicate content penalization.

[helen]

Duplicate of #20496.

[amit]

Patch for Ticket #23344