Confluence is shipped with Postgres JDBC4 instead of JDBC41

From the page https://jdbc.postgresql.org/download.html:

If you are using the 1.6 then you should use the JDBC4 version. If you are using 1.7 or 1.8 then you should use the JDBC41 version.

Since Confluence 5.8.x, Java 8 is supported, but we still ship with PostgreSQL 9.2 JDBC4

Workaround

Download the JDBC41 driver from http://jdbc.postgresql.org/download.html and replace the existing postgreSQL driver in $Confluence_Install/confluence/WEB-INF/lib