The 20 patches apply to vulnerabilities in Apache, Bluetooth and a number of other applications.
Some of the patches cover holes allowing hackers to remotely attack systems. In particular the Apache vulnerability, "contains a buffer overflow, which if used improperly in a CGI application, could allow a remote system compromise," Apple said in its advisory.
Even though security firm Secunia, which rates vulnerabilities, said it would very difficult to exploit Apache, it does rate the patches as "highly-critical" meaning that those still using Panther should update immediately.
The flaws patched in this weeks release are already covered in Apple's new Tiger OS.
Vulnerabilities have hit the news regularly in 2005. Earlier this week SC reported The National Infrastructure Advisory Council is working towards a common advisory scheme making it easier to assess the nature of vulnerabilities.
And earlier this year SC reported Microsoft's mega-update, Service Park 2 for Windows XP, had been adopted by less than a quarter of all businesses.