Confluence 2.9.1 is a recommended upgrade which fixes some security flaws as well as other bugs. You'll find details of the fixes in the release notes.
If you are already running a version of Confluence, please follow these instructions to upgrade to the latest version:
confluence.home directory and database.
An issue was fixed in this release relating to search functionality and filtering by contributor. Authors from LDAP directories are now taken into account, however you will need to carry out the instructions to make sure all users are included in this feature.