This week, the developers of the open-source PostgreSQL database issued a "critical" update.
If you are using one of the mentioned versions, the fixes are critical. You are urged to update at your earliest opportunity.
One critical fix repairs a denial-of-service vulnerability: on Windows only, the postmaster will exit if too many connection requests arrive simultaneously. This does not affect existing database connections, but will prevent new connections from being established until the postmaster is manually restarted. The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-0105 to this issue.
Another critical fix repairs an error in ReadBuffer that can cause data loss due to overwriting recently-added pages. This applies to the 8.1 and 8.0 branches on all platforms.
If you are using one of the mentioned versions, the fixes are critical. You are urged to update at your earliest opportunity.