The hotfix release 0.8.3-2 resolves a problem with the mysqli engine when a non-standard port number or socket path is used to connect to the MySQL database. The problem was reported yesterday on the WebIssues Forums. It doesn't affect configurations where another database engine is used or where MySQL uses the default port.
Note that when applying the hotfix to version 0.8.3 or 0.8.3-1, there is no need to update the database. Just unpack the package to an appropriate folder on the server. For new installations or when upgrading from older versions, follow the instructions in the manual.