Apple has released updated versions of its Safari Web browser, in order to address a number of security vulnerabilities. The primary new version, 5.0.1, is available for Windows XP, Vista, and 7, and for Mac OS X versions 10.5.x and 10.6.x. Apple also released version 4.1.1, addressing essentially the same issues, for Mac OS X 10.4.11. Apple’s “Security Content” article has details of the vulnerabilities being patched.
The new version, which I recommend installing as soon as you conveniently can, should be available through Apple’s Software Update mechanism; alternatively, the new versions can be obtained from Apple’s Support Downloads page.
Update Wednesday, 28 July, 23:25 EDT
I did not realize it from reading the original release announcement, but the new Safari 5.0.1 version apparently does have one significant functional enhancement, in addition to its security fixes. This version includes the new framework for allowing third-party browser extensions, similar to the facility that has existed in Firefox for some time. There’s a short survey of the new feature at Wired‘s “Webmonkey” site.
Apple has also introduced a new Safari Extensions Gallery.