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.
すでに Confluence のいずれかのバージョンを実行している場合、以下の手順に従って最新バージョンにアップグレードしてください。
confluence.home ディレクトリとデータベースをバックアップすることを強くおすすめします。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.