This release contains a variety of fixes from 8.0.2, including several security-related issues.
A dump/restore is not required for those running 8.0.X. However, it is one possible way of handling two significant security problems that have been found in the initial contents of 8.0.X system catalogs. A dump/initdb/reload sequence using 8.0.3's initdb will automatically correct these problems.
The larger security problem is that the built-in character set encoding conversion functions can be invoked from SQL commands by unprivileged users, but the functions were not designed for such use and are not secure against malicious choices of arguments. The fix involves changing the declared parameter list of these functions so that they can no longer be invoked from SQL commands. (This does not affect their normal use by the encoding conversion machinery.)
The lesser problem is that the contrib/tsearch2 module creates several functions that are improperly declared to return internal when they do not accept internal arguments. This breaks type safety for all functions using internal arguments.
It is strongly recommended that all installations repair these errors, either by initdb or by following the manual repair procedure given below. The errors at least allow unprivileged database users to crash their server process, and may allow unprivileged users to gain the privileges of a database superuser.
If you wish not to do an initdb, perform the same manual repair procedures shown in the 7.4.8 release notes.