Andrew nacin describes it in the post:
The release addresses a number of issues and provides two additional enhancements:
Two moderate security issues were fixed that could have allowed a Contributor- or Author-level user to gain further access to the site.
One information disclosure issue was addressed that could have allowed an Author-level user to view contents of posts they should not be able to see, such as draft or private posts.
Two security enhancements were added. One improved the security of any plugins which were not properly leveraging our security API. The other offers additional defense in depth against a vulnerability that was fixed in previous release.
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